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Book 



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Handbook on Engineering. 



THE PRACTICAL CARE AND MANAGEMENT 



OF 



DYNAMOS, MOTORS, BoYLERS^NGINES, PUMPS, INSPIRA- 
TORS AND INJECTORS, REFRIGERATING MACHINERY, 
HYDRAULIC ELEVATORS, ELECTRIC ELEVATORS, 
AIR COMPRESSORS, ROPE TRANSMISSION AND 
ALL BRANCHES OF STEAM ENGINEERING. 



BY 

HENRY C. TULLEY, 
Engineer and Member Board of Engineers, St. Louis. 



THIRD EDITIOX. 1902. 
Bevised and Enlarged. 



SOLD BY 
HENRY C. TULLEY & CO., 

Wainwright Building, St. Louis, Mo. 
PRICE, $3.50. 



TT\S\ - 



THE LIBRARY OF 
CONGRESS, 

^^o Cowes Recwved 

OCT. 28 190? 



OLASSVA.XXr «#o. 



Entered according to Act of Congress, in the year 1900, by 

HENRY C. TULLE Y, 
In the Office of the Librarian of Congress, at Washington. 



'(/ 



Copyrighted, 1902. 



Nixon-Jones Printing Co 

215 Pine Street, 

St. Louis. 



INTRODUCTION. 

The object of the writer in .preparing this work has been to 
present to the practical ^engineer a book to which he can, with 
confidence, refer to for information regarding every branch of 
his profession. 

Up to the date of the publication of this book, it was impossi- 
ble to find a plain and practical treatise on the steam boiler, steam 
pump, steam engine, and ? dynamo, and how to care for them; 
electric and hydraulic elevators, and how to care for them ; and 
all other work that an engineer is apt to come in contact with in 
his profession. 

An experience of over twenty-five years with all kinds of en- 
gines and boilers, pumps, and all other kinds of machinery, ena- 
bles the writer to fully understand the kind of information most 
needed by men having charge of steam engines of every descrip- 
tion, and what they should comprehend and employ. 

With this object in view, the writer has carefully made note of 
his past experience, and has also made note of things that came 
to his notice while visiting different engine rooms, and accord- 
ingly, has taken up each subject singly, excluding therefrom, 
everything not strictly connected with steam engineering. 

Particular attention has been given to the latest improvements 
in all classes of steam engineering and their proportioning, ac- 
cording to the best modern practice, which, it is hoped, will be 
of great value to engineers, as nothing of the kind has heretofore 
been published. 

This book also contains ample instructions for setting up, lining, 
reversing and setting the valves of all classes of engines. 

THE AUTHOR. 

(iii) 



CONTENTS. 



For Alphabetical Index to Subjects, see page 893. 



CHAPTER I. 

PAGE. 

THE ELEMENTARY PRINCIPLES OF ELECTRICAL MA- 
CHINERY 1 

A permanent magnet 1 to 2 

Two-bar magnet 3 to 6 

A magnet needle ....... e 3 

Magnetic lines of force ....... . . . 6 

Lines of force G to 14 

Magnetic force 13 

To find the lifting capacity of a magnet 13 

CHAPTER II. 

THE PRINCIPLES OF ELECTROMAGNETIC INDUCTION 14 to 22 
The armature cores 23 to 27 

CHAPTER III. 

TWO-POLE GENERATORS AND MOTORS 27 

The simplest type of armature winding 27 to 29 

Two-pole generators and nntors 27 to 30 

The g neral arrangement of the field and armature in a two-pole 

machine 33 to 36 

The reason why brushes are set differently on motors than on 

dynamos 36 to 37 

V 



VI CONTENTS. 

CHAPTER IV. 

PAGE. 

MULTIPOLAR MACHINES 38 

Multipolar machines 38 to 39 

Setting the brushes on a four-pole machine 40 

Setting the brushes on an eight-pole machine 41 

The lap and wave winding for four-pole machine . . . . . 42 to 40 

CHAPTER V. 

SWITCH BOARD, DISTRIBUTING CIRCUITS, AND SWITCH 

BOARD INSTRUMENTS 47 

Generators of the constant potential 47 to 48 

The switch-board arranged for two generators of the shunt 

type 49 to 51 

Switch-board for three-wire system 56 to 57 

To wire a large building with a lighting and power system . 58 to 60 

The ammeters 60 

Circuit breakers c .... 62 'to 63 

The electromotive in volts force, etc. 63 

CHAPTER VI. 

ELECTRIC MOTORS 64 

Motors and their connections 64 to 73 

The strength of an electric current, etc 73 

The watt 73 

The ampere 73 

Candle power 73 

CHAPTER VII. 

INSTRUCTIONS FOR INSTALLING AND OPERATING SLOW 

AND MODERATE SPEED GENERATORS AND MOTORS . . 74 

To remove the armature 74 

Assembling the parts 74 

Filling the bearings 74 

To complete the assembly 74 

Starting 74 

Care of commutator 75 



CONTENTS. Vll 

PAGE. 

If commutator gives trouble ........ 7(5 

General directions for starting dynamos ......... 7<>, 77 

Bringing dynamos to full speed 77 

Connecting one dynamo with another . . . . ■ 78 

Switching dynamos into circuit 78 

How dynamos may be connected together 78 

Dynamos in parallel . . 79 

Directions for running dynamos and motors 80 

Precautions in running dynamos 81 

Personal safety 81 

CHAPTER VIII. 

WHY COMMUTATOR BRUSHES SPARK AND WHY THEY DO 

NOT SPARK 82 to 84 

The way in which the current is shifted, etc 84, 85 

Diagram illustrating the same 85 

If the commutated coil, etc 86 

Even when the machine is properly proportioned, etc 87 

Sparking 87 to 9 L 

Noise 91 to 92 

Heating in dynamo or motor . 93 to 94 

The effect of the displacement of the armature 94 to 98 

Table of carrying capacity of wires 99, 101 

Insulation resistance 100 

Soldering fluid 101 

Table showing the size of wire of different metals that will be melted 
by currents of various strengths . 102 

CHAPTER IX. 

INSTRUCTIONS FOR INSTALLING AND OPERATING APPA- 
RATUS FOR ARC LIGHTING, BRUSH SYSTEM 103 

Theory of .the Brush arc generator 103 

Bipolar Brush arc generators 105 

General data on bipolar Brush arc generators 10(> 

Connections of No. 7k and No. 8 bipolar generators 107 

Automatic regulator for bipolar Brush arch generators 108 

Multipolar Brush arc generators 110 



Vlll CONTENTS. 

PAGE. 

General data on multipolar Brush arc genera' o s Ill 

Method of suspending armature Ill 

Method of handling the magnet yoke 112 

Setting the brushes 112 

Care of commutator * 114 

Connections of multipolar Brush arc generators 114 

Connections of Nos. 8£, 9, 10 and 11 Brush arc generators, single 

circuit, clockwise rotation with form 1 regulator 115 

Form 1 regulator for multipolar Brush arc generators 116 

Connections of Brush controller • 118 

Starting the multipolar Brush arc generator with form 1 regulator . 120 

Form 2 regulator for multipolar Brush arc generators 120 

Adjustment of form 2 regulator 123 

Starting the multipolar Brush arc generator with form 2 regulator . 123 

Form 3 regulator for multipolar Brush arc generators 124 

Form 4 regulator for multipolar Brush arc generators 125 

Ammeter 125 

Instructions for installing and operating improved Brush arc lamps . 125 

Connections for improved Brush arc lamps 128 

Diagram of same 128 

Personal safety 129 

Table showing relative resistance of metals at temperature of 70 

degrees F 130 

View of the Thomson-Houston Standard Arc dynamo arranged for 

right-hand rotation 131 



CHAPTER X. 

INSTALLATION OF ARC DYNAMOS 131 

Diagram of connections for arc lighting system 133 

Diagram of connections for rheostat 134 

View of controller for arc dynamos 135 

Testing arc light dynamos 137 

Diagram showing commutator segments and brush holders, etc. . . 138 

Table of leads * 140 

Diagrams showing best position of air blasts and jets on L D and 

M D dynamos . . 141 

Directions for setting the air blast, etc. . . . • 142 



CONTENTS. IX 

PAGE. 

Some troubles which 'may be met and their causes — reversal of 

polarity 142 

King armatures 144 

Standard plug switchboard for 6 circuits 147 

Switchboards • 147 

View of the back of switchboard 148 

View of meter for station use 149 

Connections for watt meters for series arc circuits 149 

Watt meters 150, 151 

Instructions for the installation and care of arc lamps . . . . .151 

View of interior of M arc lamp 150 

Starting the lamps 152 

Diagram of connections for M and K arc lamps 152 

Instructions for repairing, testing and adjusting arc lights . . . .153 
Table of magnetizing force in ampere turns required per inch of 
length of magnetic circuit 159 

CHAPTER Xa. 

INCANDESCENT WIRING TABLES 160 to 168 

Amperes per motor table . 169,170 

Volts lost at different per cent drop 171, 172 

Amperes per lamp table 173 

Approximate weight of il O. K." triple braided weatherproof copper 

wire 174 

Table showing difference between wire gauges in decimal parts of an 

inch 175 

Electric light conductors table 176 

CHAPTER XI. 

THE STEAM ENGINE 177 

The selection of an engine . . . . , 177 

The gain by expansion . 183 

Table of cut-off in parts of the stroke 183 

The steam engine governor 183 and 194 

The fly-wheel 184 

Horsepower 185 

Care and management of a steam engine .......... 185 



X CONTENTS. 

TAGE. 

Lubrication of an engine 186 

Selecting an oil for an engine 187 

The piston packing 187 

Crank-pins 188 

Connecting rod brasses 189 

Knocking in engines 181) to 190 

The main bearings 190 to 192 

Repairs of engines 191 

Fitting a slide valve 191 

Eccentric straps 192 

Heating of journals 193 

Automatic engines .191 

To find the dead centers . . . . • 195 

View of tandem compound engine and its foundation 198 

How to line an engine 199 to 203 

View of twin tandem compound engine, showing arrangement of 
piping 200 

CHAPTER XIa. 

Directions for setting up, adjusting and running the improved Cor- 
liss steam engene 205 

Adjustment of Corliss valve gear with single and double eccentrics. 206 

Adjustment with two eccentrics . • 215 

The compound engine 222 

Horse power of compound engine 232 

Condensing engines . 232 

Condensers 235 

Setting the piston type of valve 238 

Setting the cut-off valve 243 

Flat valve riding cut-off 245 

CHAPTER XII. 

THE STEAM ENGINE — CONTINUED 251 

What is work 251 

What is power 251 

Horse power of an engine 252 

General proportions of engine 252 



CONTENTS. XI 

PAGE. 

Rules for weights of fly-wheels 253 

View of the Russell engine 254 

Setting the valves of Russell engines 254 

View of the Porter- Allen engine 258 

Description of the Porter-Allen engine . ' 259,271 

Directions for setting the valves, and running the Porter- Allen 

engine 271, 273 

Specifications for centrally balanced Centrifugal Inertia Governor 273, 275 

The Armington and Sims engine 275 

Setting the valve in an Armington and Sims engine 275 

The Harrisburg engine 276 

The care and management of the Harrisburg engine .... 276-281 

The Mcintosh and Seymour High Speed engine . 281 

How to set the valves of an M. and S. engine 281 

The Ideal engine . . 283 

Instructions for starting and operating Ideal engines .... 283, 291 

Instructions for indicating Ideal engines 291, 292 

The Westinghouse Compound engine 293 

Instructions for starting and operating a Westinghouse Compound 

engine 292, 309 

How to set the main valve on a Westinghouse engine 301 

How to rebabbitt connecting rods : 305 

Some points on cylinder lubrication 309 

Automatic lubricators 310, 312 

Setting a plain slide valve with link motion 313,318 

Valve setting for engineers 318, 322 

View of a slide valve engine showing the point of taking steam . .321 
View of a slide valve engine showing the point of cut-off . . . .321 
View showing the position of the valve when compression 

begins 321, 322 

CHAPTER XIII. 

TAKING CHARGE OF A STEAM POWER PLANT 323 

Economy in steam power plauts 327, 329 

Priming in boilers 329 

Table of properties of saturated steam '..... 330 

High pressure steam 332, 335 

Using steam full stroke 335,337 



Xll CONTENTS. 

PAGE. 

Slide valve engines „ 337 

Regular expansion engines 338 

Automatic cut-off engines 339, 340 

The Gardiner spring governor 341,344 

The Gardiner Standard governor 342, 344 

CHAPTER XIV. 

A few remarks on the indicator 345 

The use of the indicator in setting valves, etc 346 

A card from a throttling engine 347 

A card from an automatic cut-off engine 350 

Calculating mean effective pressure 351 

The theoretical curve 353, 357 

A card from a Corliss engine 357 

A stroke card 358 

A steam chest card 359 

Eccentric out of place cards 360, 361 

Eccentric cards 361,365 

How to take an indicator diagram 365 

Cards from u Eclipse " ice machine plant 371,373 

A collection of diagrams which illustrate very nicely the peculiari- 
ties and difference in the action of throttling and automatic en- 
gines 375, 379 

CHAPTER XV. 

ECONOMY OF STEAM ENGINES 380 

The question whether or not more steam is used when an engine is 
made to run faster without changing either the cut-off or the pres- 
sure 380 

How to increa.se the power of a Corliss engine 381, 382 

How to increase the power of an engine having a throttling governor 383 
How to increase the horse power of an engine having a shaft gov- 
ernor 385 

How to line an engine with a shaft placed at a higher or a lower 

level 385, 387 

How to line the engine with a shaft to which it is to be coupled 
direct • . . . 387 



CONTENTS. Xlll 

PAGE. 

How to set a slide valve in a hurry 388 

A few things for an engineer to remember 388 

The travel of a slide valve 390 

Loss of heat from uncovered steam pipes 391 

Rules and problems appertaining to the steam engine . . . 392, 395 

To find the water consumption of a steam engine 395, 397 

Table of hyperbolic logarithms 397 



CHAPTER XVI. 

THE STEAM BOILER 398 

The force of steam and where it comes from 398, 400 

The energy stored in steam boilers 400, 401 

Special high pressure boilers 401 

Types of boilers 402 

Horse power of boilers • 402, 404 

The rating of boilers 404 

Working capacity of boilers 405, 406 

Code of rules for making boiler tests 407, 414 

Definitions as applied to boilers and boiler material 415 

Heat and steam • 416, 421 

Selection of a boiler 422, 425 

Boiler trimmings 426,432 

The care and management of a boiler 433, 437 

Water for use in boilers 438, 448 



CHAPTER XVII. 

USE AND ABUSE OF THE STEAM BOILER 449, 453 

Design of steam boilers 454, 455 

Forms of steam boilers 456 

Setting steam boilers 456, 457 

Defects in the construction of steam boilers 457, 459 

Improvements in steam boilers . 459, 461 

Strength of riveted seams 461, 466 

Maximum pitches for riveted lap joints 466 

Iron plates and iron rivets, double riveted lap joints . . , , . .467 



XIV CONTENTS. 

PAGE. 

Zigzag riveting and chain riveting 4<;x, 472 

Single riveted lap joints, iron plates 469 

Steel plates and steel rivets, S. It. L. J 470 

Steel plates and steel rivets, D. It. L. J 471 

Strength of stayed flat boiler surfaces 473 

Boiler stays 474, 477 

Eiveted and lap welded flues 477, 481 

Table of allowable steam pressure on flues 478, 479 

Thickness of material required for tubes 481, 486 

Table of wrought-iron welded pipe 486 

Pulsation in steam boilers 487, 488 

Weight of square and round iron per lineal foot 488 

Water columns for boilers 489 

Steam gauges 489, 490 

Safety valves 491, 499 

Table of the rise of safety valves 494 

Safety valve rules 497 

Table of heating surfaces in square feet 501 

Centrifugal force 501 



CHAPTER XVIII. 

THE WATER TUBE SECTIONAL BOILER 502 

The down draft furnace 503, 522 

View of boiler setting and furnace common in the East 513 

Vertical tubular boilers 514, 521 

Proper water column connections 515 

Table of pressures allowable in boilers 516 

Fire line in boiler settings 520 

Proper location of gauge cocks 521 

Number of bricks required for boiler setting ... - 522 

Specifications for a sixty-inch 6-inch flue boiler 524 

Banking fires . 531 

Instructions for boiler attendants 532 

Rules and problems anent steam boilers 536 

Steam jets for smoke prevention 542 



CONTENTS . XV 

CHAPTER XIX. 

PAGE. 

THE STEAM PUMP 544 

The Worthington Compound pump 544 

View of steam valves properly set 545 

The Deane steam pump 546 

View of steam valves properly set 547 

The Cameron steam pump . 548 

Explanation of steam end 548 

View of steam valves properly set . 548 

The Knowles steam pump 550 

Explanation of steam valves 550 

View of steam valves properly set 552 

The Hooker steam pump 553 

Operation of the Hooker pump 553 

View of steam valves properly set 555 

The Blake steam pump 555 

Operation of the Blake pump 556 

View of steam valves properly set 558 

Miscellaneous pump questions and answers ...... 559 and 603 

How to set the steam valves of a duplex pump 567 

View of steam valves properly set . .568 

Proper pipe connections 569 

View of pipe connections 570 

Pumps refusing to lift water 577 

Corrosion in water pipes 579 

Pumping acids 579 

Selecting boiler for a steam pump 580 

The Worthington water meter . . .581 

Table of water pressure due to height 582 

Table of decimal equivalents of 16ths, 32nds and 64ths of an inch . 583 

Capacity of tanks in U. S. gallons 584 

Capacity of square cisterns in U. S. gallons 585 

Weight of water 585 

Cost of water 587 

Loss by friction of water in pipes 588 

How water may be wasted 589 

Ignition points of various substances 589 



XVI CONTENTS . 

CHAPTER XX. 

PAGE. 

THE INJECTOR AND INSPIRATOR .......... 591 

First appearance of the injector 592 

Range of the inspirator and injector 592 

General directions for piping injectors 594 

Care and management of injectors 599,602 

Directions for connecting and operating the Hancock inspirator . . 597 

Waterbetween32°and212° Fah 602 

Steam pump problems 603 

Water pipe problems - . . . . 608 

CHAPTER XXI. 

MECHANICAL REFRIGERATION ...,;. 619 

How it is produced 619 

Principles of operation 620 

Operation of apparatus 620 

Function of the pump and condenser 621 

What does the work 621 

Mechanical cold easily regulated 622 

Utilizing the cold 622 

Brine system > 622 

Direct expansion system 623 

Rating of the machine in tons capacity 623 

Difference in the ratings 623 

Unit of capacity 624 

The preparation of brine 624 

Insulation of buildings 626 

Perfect insulation . . . 628 

A few tests for ammonia 629 

Testing for water by evaporation 629 

Lubrication of refrigerating machinery 630 

Effects of ammonia on pipes 631 

To charge the system with ammonia 632 

Process or mechanical refrigeration 633 

View of the "■ Eclipse " compressor 635 

The compressor pumps 636 

The De La Vergne horizontal compressor 636 

Pipe arrangement for vaults 637 



CONTENTS. XV11 

PAGE. 

Diagram of the De La Vergne system 638 

Rating machines for ice making 638 

A complete ice making plant 639 to 640 

View of double acting compressor 640 to 644 

A complete refrigerating plant 642 

Complete cycle standard De La Vergne vertical machine .... 643 

CHAPTER XXII. 

SOME PRACTICAL QUESTIONS USUALLY ASKED OF ENGI- 
NEERS WHEN APPLYING FOR LICENSE 646 

Reasons why pumps do not work 647 

Priming in boilers 648 

Foaming in boilers 648 

In case of low water in a boiler 649 

Best economy in running an engine 650 

What is valve lead 653, 666, 668 

What is meant by expansion of steam 654 

Describe the Corliss valve gear 654 

What is lap on a valve 654, 666, 670 

Taking up lost motion in an engine 654 

Direct and indirect valve motion 668 

To test a piston for leakage of steam 669 

CHAPTER XXIII. 

INSTRUCTIONS FOR LINING UP EXTENSION TO LINE SHAFT 672 

Simplicity in steam piping 674 

Cutting pipe to order 675 

Feed water required for small engines 676 

Heating feed water 676 

Rating boilers by feed water 676 

Weights of feed water and of steam 677 

Feed water heaters 678 

Table showing the units of heat required to convert one pound of 
water at the temperature of 32° Fah., into steam at different pres- 
sures 679 

Table showing gain in use of feed water heaters, and percentage of 
heat required to heat water for differe it feed and boiling tempera- 
tures, as compared with a feed and boiling temperature of 212° . 680 



XV111 CONTENTS. 

PAGE. 

Pure water 681 

The temperature and pressure of saturated steam 684 

Something for nothing • . 686 

Melting point of metals 687 

Chimneys 688 to 694 

Weight of steel smoke stacks per linear foot 694 

CHAPTER XXIV. 

HORSE POWER OF GEARS . . . 695 

Table of H. P. of shafts 697 

Prime movers 697 

Wheel gearing 698 

The pitch line of a gear wheel 698 

To find the pitch of a wheel 698 

To find the chordal pitch 699 to 703 

To find the diameter of a wheel 699 to 703 

To find the number of teeth for a wheel 699 to 703 

To find the proportional radius of a wheel or pinion 700 

To find the diameter of a pinion 700 

To find the. circumference of a wheel 700 

To find the number of revolutions of a wheel or pinion . . 700 to 701 

Stress on gear teeth 705 

A train of wheels and pinions 701 

Table of diameters and pitches of wheels 70 1 

Curves of teeth 705 

Construction of gearing 70(5 

Bevel wheels 707 

Worm-screw 708 

Proportions of teeth of wheels 709 

To find the depth of a cast-iron tooth 709 

To find the horse-power of a tooth 710 

Calculating the speed of gears 710 

When time must be regarded 711 

Table of weight of a square foot of sheet iron 712 

Screw cutting " 713 

Transmission of power by manila rope 714,812,813 

Decimal equivalents of one foot by inches 714 

Table of transmission of power by wire ropes 715 and 814 



CONTENTS. XIX 

CHAPTER XXV, 

PAGE. 

ELECTRIC ELEVATORS 716 

The Otis elevator . . .71(3 

Belt driven elevators , . .. 716, 725 

Direct connected elevators 717, 730 

The motor-starting switch 719 

The elevator machine brake 720 

The main hand rope 721 

View of connections of gravity motor controller to elevator . . . 722 
View of connections of gravity motor controller with separate rope 

attachment 723 

Direct connected electric elevators 730 

Automatic stops 733 

View of circuit connections • 734 

The starting resistance 735 

The switch lever ' ( 736 

Cutting out the series field coils 737 

The safety brake magnet 739 

The proper care of machines 739, 779 

How to start the car 743 

The car switch 748 

The slack cable switch 749 

Electric control for private house elevators . 749 

View of wiring for private houses 750 

The Sprague Electric Co.'s elevators 756 

View of operative circuits for Sprague screw elevator 762 

The pilot motor . 763 

Care of Sprague elevators 765 

Directions for the care and operation of electric elevators . . . .765 



CHAPTER XXVI. 

HYDRAULIC ELEVATORS 769 

How to pack hydraulic vertical cylinder elevators ....... 769 

How to set the hand cable on a iever machine 770 

How to pack vertical cylinder valves 771 

View of Otis vertical hydraulic elevator and valve chamber, and 
packing same 772 



XX CONTEXTS. 

PAGE. 

View of the Crane auxiliary and main valve, and operation of same . 775 

Automatic stop valve 776 

Leather cup packings for valves 784 

Closing down elevators 784 

Otis gravity wedge safety 777 

Care of Hale elevators 777 

Water for use in hydraulic elevators 778, 781 

Otis differential and auxiliary valve 780 

Elevator inclosures and their care 782 

Standard hoisting rope with 19 wires to the strand 783 

Cables, and how to care for them 783 

Lubrication for hydraulic elevators 785 

Belts, and how to care for them 786 

Useful information 786 

To tiud leaks in pressure tanks 786 

Decimal equivalents of an inch 787 

CHAPTER XXVII. 

THE DRIVING POWER OF BELTS 788 

The average strain or tension at which belting should be run . . . 788 

Rules and problems anent belting 788, 797 

Extracts from articles on belts, by R. J. Abernathy 790 

Transmitting power of belts 795 

Table of horse-power of belts 796,799 

Directions for adjusting belting , . . 798 

Horse power of belting 799 

CHAPTER XXVIII. 






AIR COMPRESSORS, THERMOMETERS, THE METRIC SYS- 
TEM, AND ROPE TRANSMISSION 800 

Losses in air compressors 800 

Capacity of air compressors . 800 

Contents of a cylinder in cubic feet for each foot in length . . . • . 801 

The McKierman air compressor 801 

The Bennett automatic air compressor 803 

The Ingersoll-Sergeant air compressor 803 I 

The Pohle air lift system 807 



CONTENTS. XXI 

PAGE. 

The metric system 801 

Thermometers 811 

Rope transmission . . 812 

Horse-power transmitted by hemp ropes 813 

To test the purity of hemp ropes 814 

Wire rope data 814 

CHAPTER XXIX. 

ALTERNATING CURRENT MACHINERY . . . . . . . . .815 

The principles of alternating currents . . .815 

Diagrams representing a generator of either continuous or alter- 
nating currents 817 

Diagrams showing the relations between alternating currents and 

e.m.fs 821, 825 

One reason why alternating currents vary, etc 82 5 

Diagrams showing the way in which sine curves are used, etc. . . 826 

Polyphase currents 832 

Unbalanced three-phase currents, etc 834 

Inductive action in alternating current circuits, etc 834 

The angle of lag between the current, etc 837 

By the use of condensers, etc 840 

The general principle of construction of a condenser, etc 841 

Mutual induction 842 

Transformers 844 

The action in a transformer 846 

The object in using transformers 849 

Alternating current generators 852 

Diagram illustrating a simple alternating current generator . . .854 

Alternator of the multipolar type 855 

How alternating current generators are run 859 

If an alternator is of the multipolar type 854 

A revolving field alternator 857 

An inductor alternator 858 

Alternating current generators 859 

Alternators run in parallel 860 

Starting alternators connected in parallel 861 

The way in which synchronizing lamps are connected 863 

Compensating and compounding alternators 864 



XX11 , CONTEXTS. 

PAGE. 

Field magnetizing currents , 867 

Alternating current motors 867 

Two-phase revolving field synchronous motor 869 

Power factor • 870 

Induction aud other types of motors 871 

Principle of the induction motor • . . . . . .872 

Induction motors if very small 877 

Three-phase induction motors 877 

While induction motors are very satisfactory machines 878 

Rotary transformers and rotary converters 878 

Principle of the rotary transformer 879 

Alternating current distributions 882 

Starting 886 

Parallel running of alternators 887 

Types suitable for parallel operation . . . . • 887 

Division of load 887 

Compound alternators 887 

Belted machines 888 

Direct coupled machines 886 

Starting 889 

Shutting down 890 

Care of machines 890 



HANDBOOK ON ENGINEERING. 



CHAPTER I. 



THE ELEMENTARY PRINCIPLES OF ELECTRICAL 
MACHINERY. 

The operation of electric generators, or dynamos, as they are 
ordinarily called, and also that of electric motors, depends upon 
a simple relation between electricity and magnetism, which will 
be explained in a simple manner in the following paragraphs. 



JV 



Fm. 1. 



j\r 




Fig. 2. 



Fig. 4. 




Fig. 3. 



A permanent magnet, as is well known, is a bar of steel which 
possesses the power of attracting pieces of iron. These bars may 
f>e made straight, as in Fig. 1, or in the form of a U, as in Fig. 
m or in any other shape desired. The strength of a permanent 
magnet depends upon the kind of steel of which it is made, and 

1 



2 HANDBOOK ON ENGINEERING. 

also upon the temper it is given. Generally speaking, the harder 
the steel the stronger the magnet. A bar of soft steel, or wrought 
iron, cannot be made into a permanent magnet of any noticeable 
strength, but if such a bar is covered with a coil of wire, as shown 
in Figs. 3 and 4, and a current of electricity is passed through 
the wire, the bar will be converted into a very strong magnet so 
long as the current flows. As soon as the electric current stops 
flowing through the wire, the magnetism of the bar will die out. 

Magnets of the last-named type are called electro-magnets, as 
they do not possess magnet properties except when the electric 
current flows around them. Electro-magnets, when energized by 
sufficiently strong electric currents, can be far more powerful than 
the permanent magnets, and on that account they are used in 
electric generators and motors. In addition to being stronger 
magnets, the electro-magnet has the advantage that it can be 
magnetized and demagnetized almost instantly, by simply cutting 
off the exciting electric current, and on this account they can be 
used for parts of electrical machines and apparatus, for which the 
permanent magnet would be entirely unsuited. 

If we test the attractive power of a magnet, we will find that 
it is greatest at the ends, the force at the middle point being 
scarcely noticeable. A bar such as Fig. 1 or Fig. 3 might hold a 
piece of iron weighing several pounds, if presented to either end, 
while at the middle point, it might not be able to sustain more 
than an ounce or two. Owing to this fact, the ends are called 
the poles of the magnet. 

If any magnet is suspended from its center, like a scale beam, 
and allowed to swing freely, it will be found that it will come to , 
rest in a north and south position, and no matter how violently itj 
may be moved around, it will always come to a state of rest 
with the same end pointing towards the north. On this ac- 
count, the ends are called north and south poles, the north pole 
being the end that points toward the north. 



HANDBOOK ON ENGINEERING. 6 

If two-bar magnets are suspended side by side with the 
north end of one at the top and the north end of the other 
at the bottom, as is illustrated in Fig. 5, they will attract each 
other; but if both magnets had the north end at the top, they 
will push away, as shown in Fig. 6. It is evident that there is 
a good reason for this difference in action, and this reason we 
can find out by experiment. 




Fig. 5. 




Fig. 6. 



A magnet needle, such as is used in mariner's compasses, is 
simply a small magnet. If we place a magnet bar, as shown in 
Fig. 7, and then set near to it, in different positions, a compass 
containing a very small needle, we will find that in these several 
positions the direction of the needle will be about as is indicated 
by the small arrows marked b on the curved lines a a; the point 
of the arrow being the north end, or pole of the needle. The 
reason why the needle will take up these positions is that the north 
end of the bar attracts the south end of the needle, and pushes 
away the north end, just as in Figs. 5 and 6, and the south end 
of the bar acts in the same way ; so that there is a tug of war 
going on, so to speak, between the attractions and repulsions of 



4 



HANDBOOK ON ENGINEERING. 



the two ends of the bar upon the two ends of the needle, the 
result being that the position assumed by the needle is the re- 
sultant of these several actions. When the needle is near the 



.<£ ~N 



\ a 



,v 



Fig. 



*/ 



/ 







Fig. 8. 



north pole of the bar, its south end is attracted with the greatest 
force, and when near the south end of the bar, the north end ex- 
periences the greatest attraction. 

If we were to place the exploring needle in all possible posi- 
tions near the magnet and trace lines parallel with it, in these 
positions, we would obtain a large number of curves about the 
shape of those shown in Fig. 8. As these curves represent the 
direction into which the magnet needle is turned at the various 
points in the vicinity of the magnet, they represent the direction 
in which the combined forces of the two poles act at these two 
points, hence, these lines are called magnetic lines of force. 



HANDBOOK ON ENGINEERING. . 5 

When two magnets are suspended as in Fig. 5, the lines of 
force of both will be in the same direction as is indicated in Fig. 
9 by the arrow heads on the curves a a. That this is true can be 
seen from Fig. 7, in which it will be seen that the arrow heads 
point toward the south pole and away from the north pole. 
As the north pole of a magnet has an attraction for the south 
pole, we can readily see that there is an endwise pull in the 
lines of force, which tends to make them contract, like rubber 
bands, hence, we can imagine the lines a a in Fig. 9 to contract 
and thus draw the two magnet bars together. 

The repulsion of the two magnets, when the north poles are at 
the same end, is illustrated in Fig. 10. Here we see that the lines 
of force passing on the outside of the bars, as indicated by 
lines a a, are unobstructed, and can assume their natural posi- 



es 





Y 


sr- *n 


S 


■ 


s 




N 



Flo-. 9. 







\^o 



Fior 10. 




tion, but those that pass between the bars, along line c, are 
pressed out of position. If we assume that the lines of force 
make an effort to retain their position, like so many wire 



b HANDBOOK ON ENGINEERING. 

springs, then we can see that the repulsion is due to the effort that 
the lines make to assume their natural form in the space between 
the bars. 

Magnetic lines of force have no real existence, they simply in- 
dicate the direction in which the force acts, but if we keep this 
fact in mind, it helps us to understand magnetic actions, if we 
treat the lines of force as if they were something real. This fact 
will become more evident as we proceed. 

Lines of force always j)ass from the north to the south pole 
through the space between these poles, and through the magnet 
itself, they are assumed to pass from the south to the north pole. 
The form of the lines of force depends upon the relative position 
of the north and south poles. In Fig. 9 they are curved, as 



s # 


== 


s jy 



Fig. 11. 

the magnets are placed side by side, but if the bars were arranged 
end to end, as in Fig. 11, the lines of force would be straight, as 
is shown at a. From the north end of the right side magnet, the 
lines of force would pass in curved line, as in Fig. 10, to the south 
pole of the magnet on the left side, thus completing the magnetic 
chain, or circuit, as it is called. 

If we take the two magnet bars of Fig. 11 and stand them on 
end, as in Fig. 12, and suspend a bent wire C in the manner 
shown, effects can be produced that are interesting and instruct- 
ive, as they illustrate the principle upon which generators and 
motors act. The wire C should be journaled at D D, so as to 
swing with as little friction as possible, and its ends are to be con- 
nected with a battery B, by means of fine wires a and b; a switch 
being provided at c so as to stop the flow of current when desired. 



HANDBOOK ON ENGINEERING, 



I* the switch c is opened, so that no current flows through 0, the 
latter will not be disturbed, and if we give it a swing, it will oscil- 
late back and forth, like a clock pendulum, and in a few seconds 
come to rest in the position in which it is shown. If the switch 
is closed, C will at once swing out of the stream of magnetic lines 
of force and will remain in that position as long as the current 
from the battery passes through it. The direction in which C 




Fig. 12. 



will swing will depend upon the direction of the current through 
it. If with the wires a and b connected with the battery, in the 
manner shown, the wire C swings to the right side, then if a is 
connected with e, and b with d, the direction of swing will be 
reversed ; that is, C will swing toward the left. 

From this experiment we see that the magnetic lines of force 
can develop a repulsive force against an electric current, and that 
the direction of the repulsion depends upon the direction of the 



8 



HANDBOOK ON ENGINEERING. 



electric current with respect to the direction of the lines of force. 
We now desire to know why this repulsion is developed, and this 
we can ascertain by the following experiments : — 

If we arrange three wires as shown in Figs. 13, 14 and 15, so 
as to run north and south, the upper end being north, and place 
oyer these magnet needles D D D, pivoted at e e e, we will find 
that if there is no current flowing through the wire, the needle 
will point toward the north, or be parallel with the wire, as is 





Fig. 13. 



14. 



Fig. 15. 



shown in Fig. 14. If the current runs through the wire from 
south to north, the north end of the needle will swing to the right, 
as in Fig. 15, and if the current runs through the wire from north 
to south, the north end of the needle will swing toward the left, 
as in Fig. 13. From this we see that an electric current can 
repel a magnet, and that the direction in which it repels it depends 
upon the direction of the current. 

If we stand the three wires on end, as shown in Figs. 16, 17 
and 18, in which ABC represent the wires as seen from above, 
we will find out more about the relation between electric currents 



HANDBOOK ON ENGINEERING. 



9 



and magnets. If we place four small magnet needles around each 
one of the wires, as shown at a a a a, we will find that those 
around the center wire, through which no current flows, will all 



/ 
a 

\ 



"fa 



/ 



A 



a \ v • a \ ^ 



a 



Fig. 16. 



Fig. 17. 



\ 



Fig. 18. 



point toward the north, as shown, while those around the wire 
Fig. 16, through which a current flows upward, that is, away from 
the center of the earth, will point in a direction opposite to that 
in which the hands of a clock move; and in wire Fig. 18, in 
which the electric current flows down toward the center of the 
earth, the north ends of all the needles will point in the direction 
in which the hands of a clock move, that is, just opposite to those 
in Fig. 16. 





Fig. 19, 



Fig. 20. 



From these actions, we infer at once that when an electric 
current flows through a wire, the latter becomes surrounded 
with magnetic lines of force, as is illustrated in Figs. 19 and 20, 



10 HANDBOOK ON ENGINEERING. 

and that there is a fixed relation between the direction of the 
current and that of the lines of force. At A, Fig. 19, the direc- 
tion of the lines of force is shown for a current moving up- 
ward, and at J3, Fig. 20, the direction of the lines of force is 
that due to a current moving downward through the wire. 

Inasmuch as an electric current flowing through a wire is 
surrounded by magnetic lines of force, we can say that a com- 
plete electric current consists of two parts, one the current proper, 
which traverses the wire, and the other the magnetic casing which 
envelops the wire. It is the action between the latter part of the 
current and the lines of force of magnets that develops the 
current in a generator, or the power in a motor. 

With the aid of Figs. 21 and 22, we can now show how the 
force is developed that thrusts the wire to one side in Fig. 12. 
The lines of force of the magnet, which constitute what is called 
the magnetic field, will flow from the north pole at the top to the 
south pole at the bottom, as is shown in Figs. 21 and 22. If the 
electric current flows through the wire C from the back toward 
the front, the lines of force developed around it will have the 
direction shown in Fig. 21. As lines of force cannot flow in op- 
posite directions in the same space, the lines of the field will swing 
over to the left side of the wire, but in doing so they will be 
stretched out of the straight form, and they will also push the 
lines surrounding the wire out of their central position. Under 
these conditions, which are illustrated in Fig. 21, the effort made 
by the field lines to straighten out, together with the effort made 
by the wire lines to return to the central position, will develop a 
thrust between the wire and the field, and thus force the former 
out toward the right side. 

If the direction of the current through the wire is reversed so 
as to flow from front to back, the direction of the lines of force 
around the wire will be reversed, and will be as in Fig. 22. Under 
these conditions, the lines of force of the magnetic field will 



HANDBOOK ON ENGINEERING. 



11 



swing over to the right side of the wire, and thus the thrust will 
be in the opposite direction. 

Fig* \ 2 represents the principle of an electric motor in its sim- 
plest form, and from it we see that the force that causes the 
armature to rotate is developed by the repulsion between the mag- 
netism of the field magnet and the magnetism that surrounds the 
wires wound upon the armature. 








Fig. 21. 



Fig. 22. 



It is self-evident that if we undertake to force the wire C 
through the magnetic field in the opposite direction to that in 
which it swings, we will have to make an effort to do so ; that is, 
if we try to move the wire from right to left in Fig. 21, or from 
left to right in Fig. 22, we will have to apply power. Now nature 
is a strict accountant and does not allow any power to be lost ; 
therefore, all the energy we expend in moving the wire through 
the magnetic field must appear in some other form, and the form 
in which it appears is as an electric current that is generated in 



12 HANDBOOK ON ENGINEERING. 

the wire. If we were to remove the battery in Fig. 12 and put 
in its place an instrument to indicate the presence of a current in 
the wire, we would find that sVhen we move the latter in the 
opposite direction to that in which it moves under the influence of 
the current, we generate a current; that is, we convert the device 
into a simple electric generator. If in Fig. 21, we move the wire 
from right to left, the direction of the current generated in the 
wire will be the same as that of the current which causes the wire 
to swing in the opposite direction, that is, from back toward the 
front. As it is a poor rule that does not work both ways, we 
would naturally infer that if moving the wire from right to left 
develops a current from back to front, movement in the opposite 
direction would develop a current from front to back ; and such 
is actually the case. This fact can be demonstrated by Fig. 12. 
Suppose that in this figure we hold C stationary in the central 
position, and then pass a current through from back toward the 
front ; this current would exert a force to swing C to the right 
side. If we release the wire, it will swing to the right and as 
soon as it begins to move, the current will become weaker, show- 
ing that the movement of the wire developed therein a current in 
the opposite direction. If we force the wire over to the left side, 
the current flowing through it will begin to increase as soon as 
the wire moves. 

All the foregoing shows us that when a wire is moved through 
a magnetic field, a current will be generated in it if it forms part 
of a closed circuit, and it makes no difference whether there is a 
current already flowing in the wire or not. When the wire is 
caused to move through the magnetic field by a current flowing 
through it from an external source, the current developed in it will 
be in opposition to that which comes from the external source, 
and, as a consequence, the movement produces an actual reduc- 
tion of the strength of current flowing through the wire. The 
stronger the magnetic field and the greater the velochy of the 



HANDBOOK ON ENGINEERING. 13 

wire, the stronger the current generated in opposition to the driv- 
ing current, and, therefore, the weaker the latter. It is on this 
account that if a motor is allowed to run free, the faster it runs 
the weaker the current through it becomes, as the actual current 
in every case can only be the difference between the main driving 
current and the one developed in the wire, which latter runs in 
the opposite direction. 

Magnetic force is measured in units that are based upon the 
centimeter grame second system which is too technical to be ex- 
plained in a few words. Briefly stated a unit of magnetic force 
will exert a pull of unit mechanical force at a unit distance. 

The force of magnets is measured either by the total force of 
the magnet, or by the force exerted by each unit of cross-section. 
When the measurement is based upon the total force of the mag- 
net, the unit is called a Maxwell ; thus we speak of the total flux 
of a magnet as so many maxwells. When the measurement is 
referred to the force per unit of cross-section, it is spoken of as 
the magnetic density, or density of magnetization, and the unit 
used is called a Gauss ; thus we speak of a magnet as having a 
density of so many gausses per square centimeter, or square 
inch of cross-section. The density of magnetization is deter- 
mined by a rule given on page 46. 

The lifting capacity of a magnet can be determined by the 
following rule : — 

TO FIND THE LIFTING CAPACITY OF A MAGNET IN POUNDS. 

Multiply the area of cross-section of the magnet pole in square 
inches, by the square of the density of magnetization per square 
inch, and divide this product by 72 millions. 

This rule gives the pull for one pole. For horse shoe magnets 
double the figures. If the object lifted is not in contact with 
the poles the pull will be less than rule gives. 



14 HANDBOOK ON ENGINEERING „ 

CHAPTER II. 
THE PRINCIPLES OF ELECTROMAGNETIC INDUCTION. 

By Electromagnetic Induction, I mean the induction of electric 
currents by magnetic action. In the preceding chapter it has been 
shown that if we move a wire through a magnetic field, an electric 
current will be generated in it, providing its ends are joined, so 
as to form a closed circuit. If the ends are not joined, then there 
will be no current developed, because, an electric current cannot 
flow except in a closed circuit. When the ends of the wire are 
not joined, the movement through the field develops simply an 
electromotive force. Electromotive force is that force which 
causes an electric current to flow when there is a circuit in which 
it can flow. Electromotive force is a long-winded name and on 
that account it is always abbreviated into e.m.f., so that here- 
after when these letters are used, it will be understood that they 
stand for electromotive force. 

Metals and all other substances that allow electric currents 
to flow through them are called conductors, while glass, mica, 
wood, paper and many other similar forms of matter that do not 
allow currents to flow through them are called insulators. The 
difference between conductors and insulators is only one of 
degree, for there is no known substance that is an absolute non- 
conductor of electricity ; that is, a perfect insulator ; and there is 
no substance that does not resist to some extent the passage of a 
current — that is, there is no such thing as a perfect conductor. 
Some substances, like damp paper or wood, which stand midway 
between good conductors and good insulators, can be regarded as 
either one or the other, depending upon the service for which they 
are used. For currents of very low e.m.f., they would be in- 



HANDBOOK ON ENGINEERING. 15 

sulators, but for currents of very high e.m.f., they would be 
conductors. 

The current that will flow through any circuit when impelled 
by an e.m.f., will have a strength that will depend upon the 
amount of resistance that opposes its flow. As all conducting 
materials are not of the same degree of conductivity, their relative 
values are determined by the amount of resistance they interpose 
to the flow of the current. The resistance of a conductor is 
measured in units called ohms ; the strength of current is 
measured in units called amperes, and the e.m.f. is measured in 
units called volts. The relation between these units is such that 
an e.m.f. of one volt will cause a current of one ampere to flow 
in a circuit having a resistance of one ohm. 

When a wire is moved through a magnetic field, the e.m.f. 
induced in it will be determined by the strength of the field and 
the velocity with which the wire moves, and will not be affected 
in any way by the resistance of the circuit of which the wire 
forms a part. If the resistance is very great, the strength of 
current generated will be very low, and if the resistance is very 
low the current will be strong, but in either case the e.m.f. will 
be the same. 

If movement of the wire in one direction develops an e.m.f. 
in a given direction through the circuit, then movement of the 
wire in opposite direction will reverse the direction of the e.m.f. 
Thus, in Fig. 23, which represents a magnetic field between 
the poles N" S, if wire a is moved from right to left, it will have 
induced in it an e.m.f. that will be from back to front, and if 
the direction of motion of the wire is reversed, the e.m.f. will 
also be reversed. This will be true whether the wire is near the 
N pole or S pole. This being the case, it can be seen that if 
a represents the end of a wire moving in the direction of arrow 
d, and b the end of a wire moving in the opposite direction, the 
e.m.f. 'sin these two wires will be in opposite directions. The 



16 



HANDBOOK ON ENGINEERING. 



direction of the e.m.f. in a will be up from the paper toward 
the observer, and the direction of the e.m.f. in b will be down 
through the paper. If these two wires are secured to a shaft 
placed in the center of the field, then by the continuous rotation 





Fie. 23. 



Fig. 24. 



of the shaft, the two wires can be made to revolve around the 
circular path shown. 

If these two wires are joined at the ends, as shown in Fig. 24, 
they will form a closed loop, and although the direction of the 
induced e.m.f. in the two sides will be opposite, when compared 
to a fixed point in space, they will be in the same direction so 
far as the loop is concerned ; that is, both e.m.f. 's will develop 
currents that will flow through the wire in the same directions. 

Returning to Fig- 23 it will be noticed that if the wires re- 
volve around the circular path at a uniform velocity, their move- 
ment in the direction of line c c will not be uniform, but will be 
the greatest when the wires are in the position shown, and least, 
when they cross the line c c. In fact, when the wires cross line 
c c their motion in the direction of this line will be zero, for this 



HANDBOOK ON ENGINEERING. 



17 



is the point where the direction of movement reverses. Now, 
the magnitude of the e.m.f. induced in the wire is proportional 
to the velocity in the direction of the line c c, hence, when the 
Wires are crossing this line, the e.m.f. will be zero, and when 
ihey are one-quarter of a turn ahead of the line, the e.m.f. will 
be the highest. 

In Fig* 24 we see that in side a, the direction of the current 
is toward the front, and in b it is the reverse ; now, when a 
moves through half a turn, it will take the place of 6, and the 
direction of the e.m.f. induced in it will be the same as in b in 
the figure ; that is, it will be the reverse of what it is when pass" 
ing in front of the pole N. This being the case, it is evident 
that each time the loop makes a half -re volution, the direction of 
the current generated in it reverses. 




Fig. 25. 

As the loop in Fig. 24 is closed, the current generated in it 

would be of no practical value, but if we cut the wire at one 

side and connects the ends with rings as shown at a and b in Fig. 

25, then by means of collecting brushes c c we can take the cur- 

2 



18 



HANDBOOK ON ENGINEERING. 



rent off through the wires d d. This current, however, would 
consist of a series of impulses that would flow in opposite direc- 
tions, each one starting from nothing and increasing to its greatest 




Fig. 26 



strength when the loop reaches the position shown in the figure, 
and then declining and reaching the zero value when the loop 
reaches the vertical position. Such a current is called an alter- 
nating current, because it flows first in one direction and then in 
the opposite direction. All forms of machines that generate cur- 
rents by electromagnetic induction, develop alternating currents, 
but in the class of machines known as direct or continuous current, 
a rectifying device is used which rectifies the current before it 
reaches the external circuit. This rectifying device is called a 
commutator, and is illustrated in its simplest form in Fig 26. In 
this illustration it will be noticed that the ends of the wire, instead 
of being attached to two independent rings, placed side by side, 
are secured to two half-rings, placed opposite each other. The 
brushes c d, through which the current is taken off, are held 
stationary ; therefore, as can be readily seen, c will make contact 



HANDBOOK ON ENGINEERING. 19 

with a during one-half of the revolution, and with b during the 
other half ; and this will also be the case with brush d. Now, as 
the half-rings with which the brushes are in contact change at 
Vach half revolution, it follows that by properly setting the 
brushes, they can be made to pass from one-half ring to the other 
at the very instant when the direction of the current in the loop 
reverses, so that through each brush there will be a succession of 
current impulses, but all in the same direction. 

The device shown in Fig. 25 is a perfect alternating current 
generator, and that shown in Fig. 26 is a perfect direct current 
generator. In both cases, however, the e.m.f. induced is so 
low as to be of no practical value. To obtain serviceable 
machines, capable of developing the e.m.f. and current strength 
required in practice, it is necessary to provide very strong mag- 
netic fields and to rotate in these a large number of loops of wire. 
In order that the operation of such machines may be understood, 
I will first show how the powerful magnetic fields are obtained. 

In Fig* 27 two wires are shown as seen from the end, these 
being marked A and B. The lines of force surrounding them are 




(^|pp^ 



Fig. 28. 




in directions that correspond to opposite directions of current in 
jthe wires. In wire A, the current flows away from the observer. 
As can be seen, the lines of force of both wires have to crowd into 



20 HANDBOOK ON ENGINEERING. 

the space between the wires, for on the outside of A the two sets 
of lines would meet each other head on, and this would also be 
the case on the right side of wire B. This crowding of the lines 
of force into the space between the w T ires causes them to distort 
from their natural position and instead of being central with the 
wires, are eccentric to them. If we take a long wire through 
which a current is flowing and bend it into a loop, we will see 
that if the current flows out through one side, it will return 
through the other side, so that in the two sides of the loop the 
current will flow in opposite directions. This being the case, 
Fig. 27 can be regarded as showing the two sides of such a loop, 
and from it we find that the effect of such a loop is to concentrate 
within its interior nearly all the lines of force that surround the 
wire. 

In Fig"* 28 the two wires A and B are surrounded with lines 
of force that correspond to the same direction of current. In 
this case it will be noticed that in the space between the wires the 
lines of force flow in opposite directions ; hence, only a few of the 
lines will follow this path, simply that number surrounding each 
wire that can traverse the space without encroaching upon the 
path of the lines belonging to the other wire. If the two wires 
are very near to each other, practically all the lines of force of 
both wires will join forces, so to speak, and pass around the two 
wires. Now, if we wind a wire into a coil of many turns, the 
direction of the current in the several turns will be the same, so 
that the lines of force of all the turns will combine into one large 
stream and circulate around the entire coil side, no matter how 
many turns of wire it may contain. From this it can be seen 
that if we have a current of say ten amperes, we can make it 
produce just as powerful magnetic effect as a current of one 
thousand amperes, by simply increasing the number of turns of 
wire in the coil. A current of ten amperes passing through a coil 
of wire containing one hundred turns, will have the same magnet- 



HANDBOOK ON ENGINEERING. 



21 



isni in effect, as a current of one hundred amperes passing through 
j a coil of ten turns, or as a current of one thousand amperes pass- 
ing through a coil of a single turn. 

If we place at the side of a wire through which an electric 
current is flowing a piece of iron, as is shown in Fig. 29, the 
effect will be that the lines of force will do longer flow in circular 
paths, as indicated by the circle a, but will be deflected in the 
manner illustrated, by the presence of the iron. If, instead of 

/ V 



A 



at 









Fig. 29. 




Fig. 30. 



the straight iron bar, we substitute a ring of iron, as in Fig. 30, 
nearly all the lines of force will be concentrated in the metal, and 
the magnetic field in the space 0, between the ends of the ring, 
will be vastly greater than at any other point. The explanation 
of these actions is that all forms of matter oppose the develop- 
ment of magnetic force, but some offer greater resistance than 
others. Iron, steel, nickel, and one or two other metals, offer 
less resistance to the magnetic lines of force than air, and are 
said to have a higher magnetic permeability. Nickel is only a 
slight improvement on air, but steel and iron are far superior, 
iron being of about two to three times the permeability of hard- 



22 



HANDBOOK ON ENGINEERING. 



ened steel, and about one thousand times the permeability of air, 
when magnetized to the density ordinarily used in practice. The 
iron in Figs. 29 and 30, therefore, becomes the path of the lines 
of force, because it interposes a much lower resistance. Owing 
to this difference in the resistance of iron and air, it is possible 
to make an iron magnet core of any desired form, and to con- 
centrate within it nearly all the lines of force developed by the 
current flowing through the wire wound upon it. The presence 
of the iron not only serves to concentrate the magnetism in it, 
but as it reduces the resistance opposing the development of 
the magnetism, it enables the field to be made vastly stronger 
than it could be with air alone, say a thousand times as great. 

If we make a magnet in the form of Fig. 31, with a coil of 
wire around the parti?, practically all the lines of force will flow to 




Fig. 31. 



the poles N S, and will pass through the air space between them. 
If this air space is nearly filled with a cylindrical mass of iron, A, 
the strength of the magnet will be increased, for, by doing this, 



HANDBOOK ON ENGINEERING. 



23 



we replace air which is a poor magnetic conductor, by iron which 
is a far superior conductor. Electric motors and generators are 
made with a cylindrical mass of iron at A, which is the armature 





Fig. 32. 



Fig. 33. 



core, and the air space between it and the faces of the poles of the 
field magnet is made just sufficient to accommodate the wire 
coils, and by this means the field strength is increased as much as 
possible. 

The armature cores are sometimes made solid, as in Fig. 32, 
and sometimes as a ring, as in Fig. 33. When they are solid, 
the lines of force cross through them in straight lines, see Fig. 
32 ; and when they are ring form, the lines follow the ring and do 
not penetrate the interior space. 

If the single loop of Fig. 24 is replaced by a coil containing 
many turns of wire, the e.m.f. induced in it will be increased in 
proportion with the number of turns of wire in the coil, so that by 
using such a coil in a field such as shown in Fig. 31, a high 
e.m.f. can be obtained. This e.m.f., however, would be alter- 
nating, and if the current were rectified by means of a commu- 



24 



HANDBOOK ON ENGINEERING. 



tator, it would not be of uniform strength, but would fluctuate 
from a maximum value to zero. Just how the current would 
fluctuate and how the construction can be changed so as to get rid 
of the fluctuation, we can explain by presenting a diagram that 
illustrates the alternating current as it flows in the armature coil, 
and the rectified current as it leaves the commutator. 

In Fig* 34, let the distance / 7i, h i, i n, along the line// 
represent half -revolutions of the coil, and let distances measured 
on the vertical line c d represent the strength of current, distances 
above /being current flowing in one direction, and distances below 
/being for current flowing in the opposite direction. Let us con- 
sider the instant when the coil is passing the point where the 
e.m.f . induced is zero ; then this instant will be represented 
by the point /, at the left of the diagram, and the curve a 
will start from this point ; as at that instant, the current which it 
represents has no value. As the coil rotates, the current begins 
to grow, and this fact we indicate by causing curve a to gradually 



Fig. 34./ 




Fig. 35. 




rise above the horizontal line. At the quarter turn, the current 
reaches its greatest strength, thus this forms the highest point of 
curve a, and is midway between / and h. From this point 



HANDBOOK ON ENGINEERING. 



25 



onward, the current declines and becomes zero, when the rotation 
of the coil has reached one-half of a revolution, which is repre- 
sented by the point h. In the next half -re volution, the current 





Fig. 36. 



Fig. 38. 



flows in the reverse direction, but has the same maximum strength 
and increases and decreases at the same rate ; therefore, the curve 
b, drawn below the horizontal line, represents the reverse current ; 
and point i corresponds to one complete revolution, so that 
beyond i the curves a and b are repeated in systematic order. 

Now, if we provide a commutator to rectify this current, all 
'we can accomplish is to turn curve b upside down and transfer it 
to the upper side of the horizontal line, as in Fig. 35 ; but, as 
will be seen, all we accomplish by this act is to obtain a current 
| that flows always in the same direction, but at each half-revo-' 
lutiou it drops down to a zero value. 

If we wind two coils upon the armature, placing them at right 
angles with each other, as is indicated by A and B in Fig. 36, 
then if the currents of these two coils are rectified, they will bear 
the relation toward each other shown at the upper line in Fig. 37, 
the a a curves in solid lines representing the current from the A 
coil, and the b b curves in broken lines, representing the current 
from the B coil. As will be seen, when one of these currents is 
zero, the other is at its greatest value, so that if we run both into 



26 



HANDBOOK ON ENGINEERING. 



the same circuit, the lowest value of the combined current would 
be equal to the maximum of either one of the single currents, 
and the maximum value would be equal to the sum of the two 
currents when the coils are on the eighths of the revolution. 



/ \ 


a Jl 


/ x \ 


a b 


- ?<r 


a Jb 


jT\ 


a 


if 


d 


i 


h 
d 


Tb 


V 








"" 








Fig 


37. 









This resulting current is shown on the lower line in Fig. 37 by 
the curve d d. From this curve we see that the number of 
fluctuations in the current has been doubled, but the variation in 
the strength is greatly reduced. If we wound four coils upon 
the armature, as indicated by A B C D, in Fig. 38, the number 
of undulations in the combined current would be again doubled, 
but the fluctuation would be very much less. If the number of 
coils is increased to twenty-five or thirty, the fluctuations in the 
current become so small as to be hardly worth noticing. 

With coils such as shown in Fig. 26, a separate commutator 
would have to be provided for each coil, and this would render 
the machine very complicated, if the number of coils were even 
six or eight; hence, in actual machines, the winding of the coils 
is modified so as to be able to use a single commutator for any 
number of coils. This construction will be explained in the 
next chapter. 



HANDBOOK ON ENGINEERING. 



27 



CHAPTER III. 

TWO POLE GENERATORS AND MOTORS. 

The simplest type of armature winding is that used with ring 
cores, and is illustrated in Fig. 39. As will be seen, it is simply 
a continuous winding all the way around the circle, the end of 
the last turn of wire being connected with the beginning of the 
first turn, so as to form an endless coil. If wires are attached at 
a and &, and a current is passed through, it will divide into two 
halves, one part flowing through the wire above a 6, and the other' 
part through the wire below a b. In the upper half of the wire, 
the direction of the current in the front sides of the turns will be 
toward the center of the ring, as is indicated by the arrow heads, 
and in the lower half it will be away from the center. If, in- 




Fio-. 39. 



Fig-. 40. 



stead of attaching wires^at a and b we place stationary springs, so 
as to press against the wire, then we could revolve the ring, and 
still the current would enter and leave the wire at the same points. 
Small armatures are often made in this way, but for regular 



28 HANDBOOK ON ENGINEERING. 

machines it is more desirable to provide a commutator as shown 
in Fig. 40 at C, and then the several segments can be connected 
with the wire at regular intervals. In the figure, the commutator 
is provided with twelve segments, and these connect with the 
armature wire at every fourth turn, so that the wire is divided 
into twelve coils of four turns each. 

The only difference between this diagram and a regular gen- 
erator armature of the ring type, is that it shows the wire coils 
spread out with a considerable space between them, and only in 
one layer, while in the actual machine, the wire is wound close 
together and generally, in several layers ; but no matter how many 
layers there may be, or how many turns in a coil, the principle of 
winding is the same. 

I have shown the ring winding first, because it is so simple 
that it can be understood with the most superficial explanation. 
The drum winding, which is used to a much greater extent, is the 
same in principle as the ring, but owing to the fact that the coils 
cross each other at the ends, it appears to be decidedly different. 
By the aid of Figs. 41 to 44, the drum winding can be made per- 
fectly clear. 

Fig* 4 J shows a ring armature core with a single coil wound 
upon it ; and Fig. 42 shows a drum core, with a single coil wound 
upon it. In the ring, only one side of the coil appears upon the 
outer surface of the armature, but in the drum, as there is no 
open space for the coil to thread through, both sides of the coil 
must be placed upon the outer surface. The side B of the coil 
may be called the live side, as it is the one from which the ends 
project, and the lower side c, may be called the dead side. Since 
only the live side of the coil has ends to be connected, it can be 
readily seen that if in the drum winding we leave spaces between 
the live sides for the dead sides, and then connect the ends of the 
live sides by jumping over the dead side between them, that we 
will have the same order of connection as in the ring winding. 



HANDBOOK ON ENGINEERING. 

B * 



29 





Fig. 41. 

The dead side of each coil adjoins the live side of a coil that is, in 
reality, half a circumference away from it; thus, in Fig. 43, the 
live side of coil a is at the top and the dead side is at the bottom ; 
while the live side of coil n is at the bottom and the dead side is 
at the top. The live sides of these two coils are on opposite sides 
of the armature, so that the coil side to the right of a is simply 




Fig. 43. 




30 HANDBOOK ON ENGINEERING. 

the dead side of a coil whose live side is on the other side of the 
diameter. In Fig. 44 the two coils a and b are adjoining coils, 
for the coil side between them is the dead side of coil n. To con- 
nect the armature, therefore, we join end 2 of coil a with end 1 
of coil b, and the end 2 of coil b would jump over a dead side and 
connect with end 1 of coil c. Coil c, however, would appear to 
be two coils ahead of 6, just as b appears to be two coils ahead 
of a. 

In winding drum armatures, the coils are generally placed in 
pairs, as shown in Fig. 43 and also in Fig. 44. The object of 
this is simply to make the ends of the armature, look more even* 
A drum armature* can be wound out of a continuous wire, by 
simply making a loop to take the place of the ends 1 and 2, and 
then skipping a space, as shown by coils a and b in Fig. 44. After 
the armature is half covered, there will be spaces left between the 
coils, these spaces being of the width of a coil ; we then proceed 
to fill up the vacant spaces, and when they are all filled, the last 
coil put in will be the proper position to connect with the first 
one wound. A little practice with a piece of twine and a wooden 
cylinder, will enable any one to find out in short order how to 
wind drum armatures. 

The two types of winding I have explained, are those used 
with two pole machines, motors as well as generators. I may 
here add that there is no difference, electrically, between a motor 
and a generator, and any machine can be used for either service. 
Motors, however, are somewhat modified in design so as to make 
them more suited to the work they have to perform. The modi- 
fication consists mainly in protecting the parts liable to be injured 
by objects falling upon them. 

The general arrangement of the field and armature in a two 
pole machine is shown in Fig. 31. The design can be changed in 
a vast number of ways, but it will always be two-pole, or bipolar, 
as it is called, if only two poles are presented to the armature. 



HANDBOOK ON ENGINEERING. 



31 



Generators and motors are arranged so that the current that 
magnetizes the field may be the whole current that flows in the 
circuit, or only a part of it. When the whole current passes 
through the field magnetizing coils, the machine is said to be of 
the series type ; this name being given because the armature wire 
and the field coils are connected in series, so that the current first 
passes through one and then through the other. If the field 
coils are traversed by only a portion of the current, the machine 



xn 




■%. 



a 




Fig. 45. 



Fig. 46. 



is said to be of the shunt type, owing to the fact that the field is 
supplied with a current that is shunted from the main circuit. 
Generators and motors are also arranged so that there are two 
sets of field coils and one is traversed by the whole current, and 
fthe other by a portion thereof. The best way to understand 
these different types of connection is by means of simple diagrams 
that show the wire coils of the field and the outline of the arma- 
ture. Such diagrams are presented in Figs. 45 to 50. Fig. 45 



32 



HANDBOOK ON ENGINEERING. 



represents the series connection, A being the armature, C the 
commutator, and M the field coil. The direction of the current 
is indicated by the arrow heads. Fig. 46 is the shunt connection, 
and the arrow heads show the direction of the currents in the case 
of a generator. As will be seen, at d the field current branches 
off from the main line and returns to it at a, after having passed 
through the field coil. Fig. 47 shows the type in which the field is 
magnetized by two sets of coils, one being in series with the main 
circuit and the other in shunt. As will be noticed, all the 
armature current passing out through wire d, goes through coil 
jp 7 , except the portion that is shunted at c, into the shunt coil M. 
This type of winding is called compound, being a combination 
of the series and shunt. When the shunt coil is connected as in 



7^ 








Fig. 47 



Fier. 48. 



Fig. 47, it is called a short shunt, and when as in Fig. 48, it is a 
long shunt. In the first case, the coil M shunts the armature 
only, and in the second, it shunts the coil F also. 



HANDBOOK OX ENGINEERING. 



33 



Fig's* 49 and 50 show the shunt and compound types for 
motors, and as will be noticed, the only difference between them 
and the generator diagrams, is that the direction of the current 




Fig. 50. 



in the shunt coils is not the same. This difference in direction is 
due to the fact that in the generator the armature generates the 
current that passes through coil M; hence, at point cZ, the cur- 
rent flows up to the main line and down to the field coil. In the 
motor, the current comes from an external source through main 
n, and thus passes from a to the armature, and also to the field 
coil, thus traversing the latter in the opposite direction. In the 
series coil F, the direction of the current is the same in both 
machines. 

Generators are made so as to keep the strength of the current 
constant, and allow the voltage to vary as the demands of the 
service may require ; or they may be wound so as to keep the 
voltage constant and allow the current strength to vary. Machines 



34 HANDBOOK ON ENGINEERING. 

of the first class are called constant current, and are 
used principally for arc lighting. Machines of the second 
class are called constant potential and are the kind used 
for incandescent lighting, for electric railways and for the 
operation of motors of every description. For constant current 
generators the series winding is used in connection with some 
kind of regulating device that prevents the current strength from 
varying more than the small fraction of an annpere. The shunt 
and compound windings are used for constant potential genera- 
tors. If the armature wire had no resistance, the shunt winding 
would enable a generator to maintain a constant voltage at its 
terminals, no matter how much the strength of the current might 
vary ; but armature without resistance cannot be made ; there- 
fore, a shunt- wound machine will develop a slightly lower voltage 
with full current than with a weak one, but the difference will 
not be more than three to five per cent. By the aid of the com- 
pound winding, the generator can be made so as to develop the 
same voltage with light or full load, and if desired, the voltage 
can be made to increase as the current increases. If a com- 
pound generator is so proportioned that the voltage is the same 
for weak and strong currents, it is said to be evenly-compounded, 
and if the voltage increases as the current increases, it is said to 
be over-compounded. If the voltage is five per cent higher, with 
full load than with no load, the generator is said to be over-com- 
pounded five per cent, and if the increase is ten per cent, it is 
said to be over-compounded ten per cent. 

The way in which a compound generator increases the volt- 
age can be readily understood from an examination of Fig. 47. 
The current that passes through the shunt coil M, is practically 
one of the same strength at all times ; therefore, the magnet- 
izing effect of this coil does not change. Through coil F the 
whole current passes, hence, the magnetizing effect of this coil 
increases as the current strength increases. Now the total field 






HANDBOOK ON ENGINEERING. 35 



magnetism is that due to the combined action of the two coils, so 
that as the action of F increases, the strength of the field in- 
creases. If F has only a few turns of wire, it will only help 
slightly to magnetize the field ; therefore, its increased effect, due 
to increase in current, will not be very noticeable ; but if F has 
many turns, it will develop a large proportion of the field magnet- 
ism, and, under this condition, the change in current strength 
will make a decided change in the strength of the field, and thus 
in the voltage, for the voltage is directly proportional to the 
strength of the field. 

In motors, the coil F can be connected so as to act with 
coil M, or against it. If both coils act together, the motor is 
compound-wound ; and if F acts against M , the motor is differ- 
entially-wound. A compound-wound motor will slow down more 
with a heavy load than a simple shunt machine, but it will carry 
the load with a smaller current, and, on this account, this wind- 
ing is commonly used for elevator motors. A differential motor 
will hold up the speed better with a heavy load than a simple 
'shunt machine, but it will take a correspondingly larger current 
!lto do the work. The differential winding is not used to any great 
extent, except in cases where it is desired to obtain as uniform a 
velocity as possible. 

In explaining the principles of armature winding, it was shown 
that the commutator brushes must make contact with the com- 
mutator on the sides, that is, that in Fig. 51, they would be 
placed on the diameter n n. In actual machines, they are either 
■j ahead of this line, as in Fig. 52, or back of it, as in Fig. 53. 
The first position is that of the generator and the second that of 
I the motor. The reason why the brushes have to be set ahead of 
iline n n in a generator, and back of the line in a motor, is that 
the armature current develops a magnetization of its own, and this 
i reacts upon the magnetism of the field so as to twist the lines of 
force out of their true path. If we look at Fig. 39, we can see 



36 



HANDBOOK ON ENGINEERING. 



that the direction of the current through the wires is such that 
the magnetizing effect produced upon the armature core is the 
same as it would be if the wire were wound in the way indicated 
by the vertical lines in Fig. 51. Now this current will develop a 
magnetization in the direction of line n n; that is, at right angles 
to the field magnetism. These two magnetic forces of the arma- j 
ture and the field, engage in a tug of war, and the result is that 
the actual magnetization that acts upon the armature wire is the 
combined effect of the two. If the strength of the field magnetism 




Fig. 51, 



Fig. 52. 



Fig. 53. 



is proportional to line c a, and the strength of the armature mag- 
netization is proportional to line c 6, then the actual magnetiza- 
tion will be equal to line c d, and in the direction d d. In Fig. 
52, which represents a generator, if the current in the held coils 
passes over the front side in the direction of arrow /. and the 
armature revolves in the direction of arrow d, then the armature 
current will be in the direction of arrow /' and the armature mag- 
netization will be in the direction of arrow //. The Held magneti- 
zation will be from A" to S, therefore, the resulting magnetization 
will be in the direction of line a a. Now the proper position for 



HANDBOOK ON ENGINEERING . 37 

Ithe brushes is on a line at right angles to the direction of the; 
field, hence, they must rest upon line c c. If the machine is a, 
motor, the only change effected will be that the direction of the 
armature current will be reversed, so that arrow / will point 
downward instead of upward, and the magnetism of the armature 
will be directed to the right as shown by arrow c. Under these 
; conditions, the actual direction of the field magnetism will be that 
[of line b 6, and upon line e e, at right angles to this the brushes 
must be set. 



38 HANDBOOK ON ENGINEERING. 



CHAPTER IV. 

MULTIPOLAR MACHINES. 

The only difference between a bipolar and multipolar machine j 
is, that the latter has two poles, and the former has two or more 
pairs of poles. In consequence of this difference in the number 




E 



Fig. 54. 

of poles, the armature winding has to be slightly modified, as will 
be presently explained. Fig. 54 illustrates a four-pole machine 



HANDBOOK ON ENGINEERING. 



39 



[and, as will be noticed, the N and S poles alternate around the 
circle. This arrangement is followed, no matter what the number 
of poles may be. 

The advantage of the multipolar construction is that it in. 
creases the capacity of the machine for a given size and weight- 
Figs. 55 to 57 illustrate the gain effected in weight. The first 
•figure shows a two-pole machine, the second a four-pole and the 
third an eight-pole, the three being of the same capacity. The 
poles of the second machine are half as wide as those of the first, 
as there are twice as many. The other parts are reduced in like 
proportion. In Fig. 57, the poles are one-quarter as wide as in 




Fig. 55. 



Fig. 56. 



Fig. 57. 



Fig. 55, as there are four times as many. On account of the 
reduction in the width of the poles, the armatures can be increased 
| in diameter as the number of poles is increased, without increas- 
jing the outside dimensions of the machine, so that in reality, 
Fig. 56 is somewhat more powerful than Fig. 55, and Fig. 57 is 
still more powerful. 

The fields of multipolar machines are wound the same as 
those of the bipolar; that is, as series, shunt or compound. 
'Figs. 58 to 60 show the three types of winding for a four-pole 
machine and Fig. 61 is a diagram of compound winding for an 
eight-pole generator. The number of commutator brushes used is 
equal to the number of poles, although with one type of armature 



40 



! i A \ DBOOK ON ENGINEERING I . 



winding, two brushes are sufficient, no matter how many pole] 
the machines may have. In practice, however, even with this 
winding, the number of brushes is generally made equal to the 
number of poles. 

With a four-pole machine the brushes can be connected in a 
simple manner, as shown in Figs. 58 to 00, but with a greater 
number of poles, two rings are generally provided, to which the 
brushes are connected in the manner shown in Fig. 61. 




Fig. 58. 



Looking at Fig* 54, it can be seen that if the current llow^ 
from the paper, under the X poles, it will flow down through 
paper, under the S poles; hence, the armature coils in a f< 
pole machine must span only one-quarter of the circumferer 
and not one-half, as in the two-pole armature. For a six-[ 
armature, the coils must span one-sixth of the circumferer 
and for an eight-pole, one-eighth, and so on, for any hig 
number of poles. 

There are two types of winding for multipolar armatures, < 
-being called the lap, or parallel winding, and the other the w 



> up 
the 
>ur- 



her 



\ e 



HANDBOOK ON ENGINEERING. 



41 




42 



HANDBOOK ON ENGINEERING. 



or series winding. Fig. 62 is a diagrammatic illustration of the 
lap winding, and Fig. 63 of the wave winding, both for four poles. 




Fig. 62. 



The small circles around the outside of the armature represent 
bars or wires, which are connected with the commutator segments 
by means of the solid lines, and with each other at the opposite 
side of the armature, by means of the broken lines. 

If we start from coil side, or bar 1 on the left, and follow the 
connections as guided by the numbers, we will finally reach 32, 
and thus come back to left side brush a, which is the starting 
point. As will be seen, bar 1 connects at the back of armature, 



HANDBOOK ON ENGINEERING. 



43 



with bar 2, and then over the front, the connection runs in the 
backward direction, to bar 3 ; thence, forward again, at the back 
! end, to bar 4, and again backward over the front, to bar 5. The 
connections, therefore, lap over each other and it is on this 
account, that it is called a lap winding. 

Fig, 63 shows the wave winding, and it will be noticed that if 
we start from bar 1 at the top, we advance around the right to bar 
2, and then we go further ahead to bar 3, and in like manner 
advance to bar 4, the connections in every case advancing in the 




Fig. 63. 



same direction around the circle. It will be further noticed that . 
the connections run zig-zag from side to side of the armature core 



44 HANDBOOK ON ENGINEERING. 

as they advance, thus forming a wave-like path for the current, 
and it is on this account that this style of connection is called 
wave winding. 

With the lap winding, the brushes a a are connected with each 
other, and so are the b b brushes. In the wave winding, two 
brushes set one-quarter of the circle from each other, will take 
the current off properly as indicated by a and b in Fig. 63, but 
four brushes can also be used. 

In Fig*. 54, the brushes are shown midway between the poles, 
while in Figs. 62 and 63, they are opposite the poles. This dif- 
ference in position is due to the fact that in the last two named 
figures, the connections between the armature coils and the conw 
mutator segments do not run in radial lines from either side, but 
one connection bends backward and the other forward. In 
actual machines, the connections are run as in these diagrams, and 
in some cases, one of the sides . runs in a radial direction ; there- 
fore, in some generators, the brushes are opposite the poles, and 
in others they are between them. 

Diagrams 62 and 63 show coils of a single turn, but by regard- 
ing the broken lines as representing the position of the end of the 
coil at front as well as the back of the armature, and the solid 
lines as simply the ends of the wire that connect with the com- 
mutator segments, they become accurate representations of coilsi 
of any number of turns. 

The coils of multipolar armatures are made on forms,- and in 
the finished state are placed upon the armature core. Some coill 
are so formed as to bend down over the ends of the armature, and 
are then given the form at the ends, shown in Fig. 64, so they 
may fit into each other. In some machines, the coils do not bend 
down over the ends of the armature, but run out parallel with 
the shaft. Armatures so wound are sometimes said to have a 
barrel winding, and the coils, if laid out upon a flat surface. 
. would present the appearance of Fig. 65 ; that is, if they con- 



HANDBOOK ON ENGINEERING. 

abed 



45 




Fig. 64. 



Fig. 65. 



taiueel more than one tarn. If of the single-turn type, they 
would look like Fig. 66, if for a lap winding; and like Fig. 67, 
if for a wave winding, the ends d d being joined and then con- 
nected with the commutator segments. 

In connecting - the field coils of multipolar machines, it is 
necessary to be careful not to make mistakes, so that some of the 



ah 



ab c 



\ 




d 

Fig. 66. 



ab *c 




& 

Fig. 67. 




46 HANDBOOK ON ENGINEERING. 

coils will act to magnetize the field in the wrong direction. By- 
studying Fig. 27 and the explanation of it, the direction of the 
magnetic lines of force with respcot to the direction of the current 
through the magnetizing coils, can be clearly understood, and 
then there will be no difficulty in determining the proper way in 
which to connect the coil ends, for all we have to do is to make 
the connections such that if one pole is N the one next to it is S. 
With two-pole machines, it is also necessary to be careful not to 
connect the field coils improperly ; that is, if there is more than 
one coil, and in most machines this is the case. 

The current that energizes a magnet is called the magnetizing 
force and is measured in ampere turns. The ampere turns are 
obtained by multiplying the number of turns of wire in coil, by 
the amperes of current flowing through it. 

All forms of matter resist the development of magnetic force. 
This resistance is called magnetic reluctance. The reluctance of 
air is much greater than that of iron or steel, but is constant ; 
that of iron and steel is not. If one thousand ampere turns 
develop a certain magnetic density in a circuit composed wholly 
of air, two thousand ampere turns will double this density. In 
iron and steel it will require much more than double the ampere 
turns to double the magnetic density. 

If in a magnetic circuit ten inches long, 100 ampere turns 
develop a certain density, it will require 200 ampere turns to 
develop the same density if the magnetic circuit is double the 
length. The table on page 209 gives the ampere turns required 
to develop different magnetic densities in magnetic circuits one 
inch long, composed of air, iron and steel. 

To find ampere turns required to develop any magnetic density 
in any magnet use following rule : — 

Multiply the figures given in the table on page 159 ; for density 
required, by length of the magnetic circuit, and the product will 
be total number of ampere turns. 



HANDBOOK ON ENGINEERING. 47 



CHAPTER V. 

SWITCH-BOARDS, DISTRIBUTING CIRCUITS AND SWITCH- 
BOARD INSTRUHENTS. 



Generators of the constant potential type are made so as to 
develop a certain voltage at a given velocity, but in some cases it 
is not practicable to run them at the exact speed for which they 
are designed ; and in others, it is desired to vary the voltage 
slightly, hence, all machines are provided with means for chang- 
ing the e.m.f . slightly. This regulating device is also necessary 
in cases where the load is for a time light, and for the balance of 
the time heavy; for, as we have shown, the voltage will vary to 
some extent with changes in the strength of the current. If 
the generator is at some distance from the points where the cur- 
rent is used, the drop of voltage in the lines will be greater with 
strong currents ; hence, when the load is heavy, it is necessary to 
increase the voltage developed by the generator. As it is not 
advisable to change the speed of the engine, the variation of volt- 
age is obtained by changing the strength of the current that 
-flows through the shunt field coils, and this is accomplished by 
providing a resistance that can be cut in or out of the shunt coil 
, circuit, as is illustrated in Fig. 68, in which R represents the 

resistance, or field regulator, as it is called. When the lever is 
if ■ " 

moved to the extreme left position, all the regulator resistance is 

cut out of the circuit, and then the voltage of the generator is 
' the highest that can be obtained with the speed at which it is run- 
ning. When the lever is moved to the extreme right, all the 
, resistance of the regulator is introduced into the shunt coil cir- 
cuit, and then the voltage is the lowest. By placing the lever in 



4<s 



HANDBOOK ON ENGINEERING. 



intermediate positions between the extremes right arid left, differ- 
ent voltages may be obtained. 

To be able to operate a generator furnishing current to a sys- 
tem of distributing wires, it is necessary to have a number of 




Fig. 68. 



instruments and other devices, included in the circuit, some of 
which are absolutely indispensable, and others of which are simply 
conveniences, and may be looked upon as luxuries. The various 
devices required are shown in Fig. 69. The generator is shown 
at jf, and ate the held regulator is placed, and it is connected 
with one of the generator armature terminals and with one end 
of the shunt coil wires by means of wires d d. The wires c c 
run from the generator terminals to the voltmeter F, and thus 
enable us to see what the voltage is at all times. Wires a and h 
convey the current to the external circuit, with which they can be 
connected or disconnected by means of switches ss ss. At. Ian 
ammeter is placed which indicates the strength of current in 



HANDBOOK ON ENGINEERING. 



49 



amperes. The ammeter can be placed in either a or b, as the 
sane strength current flows in both. At// safety fuses are pro- 
vided, so as to open the circuit in case the current becomes so 
strong as to be capable of overheating the generator wire. If one 
of the iine wires runs out into the open air, and is carried along on 
poles, ve will have to provide a lightning arrester, as shown at 7i, 
this being connected with the ground as at g. If both lines run 
into the open air, an arrester must be placed in both ; and if 
both are confined to the interior of a building, no arresters will 
be required. From the points m m branch circuits may be run 
off in as many directions as necessary, and by providing switches 
s s, these can be connected or disconnected from the main line 
when desired. 

This crude arrangement would enable us to operate the system 
successfully, but it would not be so convenient as a more methodi- 




cal grouping of the several devices and instruments. It repre- 
sents the way things were done in the early days of electric light- 
ing, but at the present time, instead of having the several parts 
scattered about in a helter-skelter fashion, they are all assembled 

4 



50 



HANDBOOK ON ENGINEERING. 



upon a large panel, which is called a switch-board. Fig. 70 gives 
the general arrangement of wiring and location of devices for a 
simple board arranged for one generator feeding into five external 




Fig. 70. 



circuits. The ammeter and voltmeter are placed at the top of the 
board, and directly under these are arranged five switches, s, 
which control the external circuits. One of these circuits is indi- 



HANDBOOK ON ENGINEERING. 51 

cated by the lines n p, ff, being safety fuses. The wires i i con- 
vey the main current from the generator to a circuit breaker D, 
which is simply a switch that is constructed so that it will open 
automatically when the current becomes too strong. From the 
circuit breaker, the current passes through wires a and b to the 
main switch F, and by wire c, it runs from here to the ammeter 
A and from the latter by wire d to a rod 1 which is called a bus 
bar. The upper side of the main switch is connected directly 
with bus 2. The voltmeter is connected with two busses by the 
wires e e. The field regulator is located back of the board at B, 
and is connected in the shunt coil circuit by means of wires h h. 
The switch of the regulator R is connected with a hand-wheel on 
the front of the switch-board, so that the attendant can watch 
the voltmeter as he turns the wheel and thus see just what effect 
the movement is producing on the voltage. 

In addition to the devices shown in Fig. 70, we can, if desired, 
provide a recording ammeter, a recording voltmeter and a watt- 
meter ; the first two would give us a record of the amperes and 
volts for a certain length of time, generally 24 hours, and the 
last one would register the amount of electrical energy. We 
could also provide ammeters for each one of the distributing cir- 
cuits, so as to know the strength of current in each one. 

If we desire to arrange the switch-board for two generators, 
and these are of the shunt type, we will require no changes in 
Fig. 70, except to provide another regulator and a main switch 
and circuit breaker for the additional machine. This arrange- 
ment of board is suitable for a single compound wound generator, 
or any number of shunt wound machines, but if we have two or 
more compound generators, the connections between these and 
the bus bars will have to be somewhat modified. 

The modifications required in a switch-board for two or more 
compound generators can be made clear by the aid of Figs. 71 
and 72. In the first figure, we can see that if the current return- 



52 



11 AN DBOO K < )N 1 : N Q 1 N E ER I N < i . 



jng from the main line through n divides into wires a and /, it 

will remain divided until it passes through the armatures ami- the 
F coils of the two machines, and thence through wires e e, it will 




reunite again in wire p. In Fig. 72, the two parts of the current 
will flow through wires d d to the single wire e, and then divide 
into wires//, and thus reach the coils F F, and, finally, through 
wires h h, reach p. In Fig. 71, if the right side armature gen- 
erates more current than the other one, the F coil of that gener- 
ator will be traversed by the strongest current, for in each machine 
the strength of current in the armature and the F coil will be 
nearly the same. Now, if the right side machine generates the 
strongesl current, it is because its voltage is the highest, but the 
fact that. its F coil will be traversed by the strongest current will 
make its voltage still higher, thus increasing the difficulty. In 
Fig. 72, the current flowing through the two F coils will be the 
same, no matter how much the two armature currents may differ, 



HANDBOOK ON ENGINEERING, 



53 



for. these come together in wire e, and- passing from this to the two 
! F coils, the current will divide in equal amounts. As can be 
seen, the effect of adding the wires d d, e and// in Fig. !2 is to 
equalize the currents that flow through the F coils, and thus pre- 
vent, as far as possible, the unequal action of the generators, j 
1 When two or more compound generators are connected so 
as to feed into the same general circuit, the connections: are 
made in accordance with Fig. 72. Fig.. 73 illustrates a switch- 
board for two compound generators, and, as will be noticed, the 
most striking difference between it and Fig. 70, is that there 
are three bus bars instead of two. One of these buryes is 
called the equalizer, and it takes the place of wires d < e ! and 




Fig. 72. 



//in Fig. 72. The equalizing connections run . from . generator 
wires /to the main switches $, and thence to bus 1. The h wires 
of the generators run to one side of the circuit breakers BE, 



54 



HANDBOOK ON ENGINEERING. 



and thence to the middle blades of the S switches, and from these 
to the bus 2. The generator wires run to the outside blades of 




Fig. 73. 



the circuit breakers, and from these to the ammeters A A, and 
thence to bus 3. The voltmeters are connected with wires h and 
/, and thus indicate the e.m.f.'s of the generators. 



HANDBOOK ON ENGINEERING. 55 

If another generator were added, it would be connected with 
the bus bars in the same way. 

In starting two or more compound-wound generators, one 
machine is started first, and then the second is run up to full 
speed, and its voltage is adjusted by means of the regulator i?, so 
as to be the same as that of the machine that is running. When 
the voltages of the two machines are equal, the main switch of 
the second machine is closed so as to connect it with the bus bars. 
This action will generally make a slight change in the voltage of 
the second machine, causing it to run up or down a trifle ; and as 
a result by looking at the ammeters, we will find that it is taking 
more or less than its share of the load. If such is the case, we 
manipulate the regulator R, until the loads are properly divided. 
Whether the voltage of the second machine will rise or fall after 
it is connected with the bus bars, will depend upon the extent to 
which it is compounded ; if slightly compounded, the voltage will 
drop, and if heavily compounded, it will rise. 

The switch-boards illustrated are adapted to what is called the 
two-wire system of distribution, but in cases where it is desired 
to transmit the current to a considerable distance, without using 
extra large wire, the three-wire system of distribution is 
employed. This system is illustrated in Figs. 74 to 76. 

Suppose we have two generators as indicated at G G in these 
diagrams, and let the direction of the current through both be 
from bottom toward the top ; then it is evident, that if we remove 
the middle wire 0, the lower machine will deliver current into the 
upper one, and if each generator develops an e.m.f. of 115 volts, 
the combined e.m.f. will be 230 volts, and this will be the 
pressure between the bottom and top wires ; but the voltage 
between either wire and the center one will only be 115. Suppose 
we have a number of lamps connected between wire P and the 
center wire 0, and an equal number of lamps between and N, 
as is shown in Fig. 74 ; then it is evident that the same amount 



56 



HANDBOOK OX ENGINEERING. 



of current will flow through both sets, and as a consequence, all 
the current that passes from the upper generator into wire P will 
go directly through both sets of lamps to the lower wire iV!, and 
thus return to the lower side of the bottom generator. Under 



{G 

6 

^ ■ fa 



*(f ■ ;&■&&$ 



IZIHB 




raja 



t ^\ VI K 



4"M 



WdQd 



■P-t 



%%9aha 



v \r v ' V 



6)^ ra)5 (o)c 



these conditions, the lamps will be acted upon by 115 volts each, 
but the current will be driven through the circuit by a voltage of 
230. Now, if the voltage is doubled, four times the number of 
lamps can be supplied with the same size wires ; hence 1 , the cost 
of line wire per lamp will be reduced to one-fourth. Suppose, 
that instead of having the lamps equally divided as in Fig. 74, 



HANDBOOK ON ENGINEERING. 57 

they are arranged as in Fig. 75 ; then since the current fed into 
the system from the upper wireP is only sufficient for five lamps, 
while there are seven lamps in the lower section, it follows that 
through wire a current sufficient for two lamps must be sup- 
plied. The way in which the currents would flow in this case is 
clearly indicated by the arrows. 

In Fig* 74, it will be seen that if we removed the middle wire, 
the lamps would not be affected, for none of the current comes 
through it; but in Fig. 75, if, we cut the middle wire, two of the 
lower lamps would be unprovided for. From this it will be seen 
that the object of the middle wire is simply to provide the extra 
current required for the side that carries the largest number of 
lamps. If the lights are so arranged that on both sides of the 
central wire the number is practically the same at all times , 
the center wire can be made very small, but such perfect balance 
cannot be obtained always, and on that accouut, the center, or 
neutral wire, as it is called, is made of the same; size as the 
others, except in large systems, in which it is sometimes not more 
than one-third the size. 

As motors require large amounts of current, they are nearly 
always made to operate with a voltage of 230, and are connected 
with the outside wires of the system, as is shown in Fig. 76, in 
which a a a a and c c c c indicate lamps connected between the 
sides and the neutral wire, and A B C are motors connected 
across the outside lines. 

When a switch-board is arranged for two generators connected 
with a three-wire system, we use three bus bars, just as in Fig. 
70, but discard the equalizing connection, and connect the 
generators with the busses in the same way as they are connected 
with wires N and P in Figs. 74 to 76. If we have a number of 
generators feeding into the three-wire system, then we connect 
each set with an equalizer bus; that is, provide two sets of 
busses, and the P and N busses of these two sets we connect 



58 



HANDBOOK ON ENGINEERING. 



with a third set in the proper order for the three-wire system, - 
and from the latter busses the external circuits are fed. 

If we desire to supply a larger building with a lighting and 
power system, we can run the wires in almost any way, providing 
we make connections with the lamps and motors, but if we adopt 



<3£ 



£ja 




Fig. 77. 



a systematic arrangement it will require less labor to operate the 
plant, and when anything goes wrong we will be able to locate 
the difficulty with much less trouble and in less time. The best 
way to accomplish this is by the use of small switch-boards 
located at different points in the building, these becoming centers 



HANDBOOK ON ENGINEERING. 59 

of distribution, from which all the lamps are supplied. The 
general arrangement of such a system can be understood from 
Fig. 77, in which B represents the main switch-board, located in 
the engine room, and e e e the several floors upon which the lights 
are located. From the main switch-board we run up four lines, 
one to each floor, and locate secondary boards at C C and D D D. 
We can also run out lines directly from the board to the lamp 
circuits as at c c c c. From the boards C 0, we run circuits to 
smaller boards, as shown at E, F, A, A, A, and b b b. From 
each one of these small boards we can run out circuits to the 
lamps. 

These small switch-boards are called panel boards or boxes, 
and also distribution boards. They are made of all sizes from 
eight or ten inches square, up to four or five feet, and are 
arranged to feed into one or two, or fifty or sixty circuits, 
supplying anywhere from five or six lights up to a thousand or 
more. 

The construction of distribution boards can be understood 
from Figs. 78 and 79, the first being arranged for the three- 
wire system, and the second for the two-wire. Fig. 78 is ar- 
ranged to feed ten circuits, and is provided with one main switch 
by means of which the entire box can be disconnected from the 
main line. The distributing circuits are provided with safety 
safety fuses on the outside wires, so that if anything goes wrong 
and the current increases to a dangerous point, the circuit will be 
open. No fuse is placed on the middle wire, as it is not neces- 
sary, and might result in cutting out both sides of the circuit 
when only one was disabled. 

Fig* 79 is a more complete panel, because each one of the six 
distribution circuits is provided with a switch, so that it is pos- 
sible to disconnect any of the circuits without interfering with the 
others. In some cases a distribution board of this kind is the 
only thing that will answer the purpose, but in others, the more 



60 



I [AND] J O 1 v O N E N G I N E E R T N G . 



simple construction of Fig. 78 answers just as well. The fuses 
in Fig 78 are shown at E F. These fuses are sometimes made so 
that they can be used as switches ; that is, they can be pulled out 




<r^i^n> 




Fig. 78. 



Fig. 71>. 



of place and thus open the circuit, and if one blows out it can be 
removed and a new fuse be put in, and then it can be replaced. 
thus {'lacing the disabled circuit in service without interfering 
with the others. 

The ammeters and voltmeters used on switch-boa ids depend 
for their operation upon the repulsion between magnetic lines of 
force. A great many different constructions are used, but most 
of them operate upon the principles illustrated in Fig. 80 or 81. 
Ira small l>ar of iron c is placed between the pole- ol' a permanent 
magnet, as in Fig. «0, it will be held in the horizontal position by 
the attraction of the magnet. If it is surrounded by a stationary 
coil of wire /;, through which a current of electricity passes, then 



HANDBOOK ON ENGINEERING. 61 

it will be under the influence of two forces, one the attraction of 
the poles JV S of the magnet, and the other the attraction of the 
lines of foice developed by the current flowing through coil b . 
The action of the latter will tend to swing the rod c into the ver- 
tical position. The force of the magnet will remain constant, but 
the force of the coil will vary with the strength of the current 
passing through it ; hence, the stronger the current the more the 
bar c will be swung around into the vertical position. If we pro- 
vide a small counter-weight, as shown in the illustration, to resist 
the action of the coil, we will have a means that will enable us to 
adjust the movement of the bar, so that it will swing around 
through a given angle for a given increase in current. If a 
pointer a is secured to c it will swing over the scale as shown, 
when c is rotated by the action of the coil. 

If coil l> is mounted so that it may swing around the center 
pivot, we can discard bar c, for then as soon as a current traverses 
b, the lines of force developed around it will be attracted by 




Fig. 80. 



those of the permanent magnet, and will exert a twisting force so 
as to place the axis of the coil parallel with the lines of force 
passing from N to S. In this case as in the previous case, the_ 



62 



HANDBOOK ON ENGINEERING. 



effort to twist b around will be proportional to the strength of 
the current, hence, the stronger the current the greater the 
swing. Ammeters and voltmeters are made on these principles, 
and the only difference in the two instruments is in the size of 
the wire used for the coils. 

Figs. 82 and 83 illustrate the principle upon which circuit 
breakers are made. In Fig. 82, suppose a current flows through 
magnet E, then it will attract the lever A, the latter being made 





C.-'> --' 



<C 



Fig. 82. 



Fig. 83. 



of iron. If the current is weak it may not develop a sufficient 
attractive force in E to lift the weight D, and in that case A will 
remain where it is. If, however, the current is increased until E 
becomes strong enough to lift D, then A will move over toward 
the magnet, and the catch " a " falling behind it, will not allow 
it to return to its former position until placed there by hand. 
When A swings over, it carries B, and thus breaks the connec- 
tion with O and opens the circuit. Thus it will be seen that by 
properly adjusting the weight D and the magnet E, we can setthe 
device so as to open the circuit whenever the current reaches a 
certain strength. This is the principle upon which circuit break- 



HANDBOOK ON ENGINEERING. 63 

ers act, but such a device as Fig. 82 would be of no service for 
lighting circuits, because the distance by which C and B are 
separated is too small to break the current. By modifying the 
construction as in Fig. 83, we can obtain a device that will give a 
wide separation at the breaking point. In this construction, the 
lever A when drawn towards the magnet, strikes the catch a, so 
as to release lever B, and then the weight D throws the latter 
down to the position shown in broken lines, thus giving a wide 
separation between F and 0. By moving the weight on the lower 
arm at A, the device can be adjusted so as to act with different 
strengths of current. 

Circuit breakers as actually constructed, do not have the 
appearance of this diagram, but they operate on the principle 
illustrated by it. 

The electromotive iu volts force developed in the armature of 
a motor, or generator, can be determined if we know the number 
of wires upon the outer surface, the number of maxwells of mag- 
netic flux that pass through the armature and the revolutions per 
second. The rule for the calculation is as follows : — 

Multiply the number of wires on the outer surface of the arma- 
ture by the maxwells of magnetic flux and by the revolutions per 
second, and divide this product by 100,000,000. 

This is the rule for two pole armatures. For multipolar arma- 
tures with series, or wave winding, use same rule making the 
flux equal to the sum of the fluxes issuing from all the positive poles. 

For multipolar armatures with a lap, or parallel winding, use 
same rule but take the flux issuing from one pole only. 

To obtain the pull in pounds of a motor armature at one foot 
radius use the following rule : — 

Multiply the number of wires on the outer surface of armature 
by the amperes of armature current, and by total number of max- 
wells of magnetic flux passing through armature, and divide this 
product by 852,000,000. See pages 13 and 46. 



64 HANDBOOK ON ENGINEERING. 



CHAPTER VI. 
ELECTRIC MOTORS. 

Motors are made so as to run at a constant velocity, or for 
variable speed. For the latter type of machine, the field coils are 
wound in series, and for constant speed the shunt winding is used. 
A motor of either kind cannot be started successfully without 
placing an external resistance in the armature circuit, because, 
when the armature is at a standstill, there is nothing but the 
resistance of the wire to hold the current back, and as a result, if 
no extra resistance is provided, the first rush of current would be 
very great. As soon as the armature begins to revolve, an e.m.f . 
is induced in its wires, and this acts in opposition to the e.m.f . 
of the line current ; that is, it acts like a back pressure, and holds 
the current back. On this account, the e.m.f. of a motor is 
called a counter e.m.f., and it is abbreviated into c. e.m.f. 

The way in which the external resistance is connected with 
a motor is illustrated in Fig. 84, in which M is the motor and 
Ii the external resistance. D is a main switch, by means of 
which the motor is connected with the main line. This switch is 
closed first, and then switch F is moved to the right until it cov- 
ers the first contact of the resistance 11. The current can then 
pass directly to the field shunt coils through wire e, and thence by 
wire a, return to the main line. The armature current, however, 
has to first pass through the resistance R, before it can reach wire 
i, and thus the armature. As soon as the armature begins to 
speed up, the switch F is advanced, step by step, and in a few 
seconds it is moved to the extreme right position, in which all the 
resistance M is cut out of the armature circuit. When F reaches 
this position, the motor should be running at full speed. 



HANDBOOK ON ENGINEERING. 



65 



If the current should stop while the motor is running, the 
machine would stop, also, and then, if the current were turned 
on again, the motor would be caught with the armature connected 
across the line without an external resistance, and as it would be 
at a standstill, the current would rise to an enormous strength. 
To prevent this, the switch F is always opened whenever the motor 
stops. The attendant may forget to do this, however ; therefore 
automatic switches have been devised that will open themselves 
whenever the current dies out. 




Fie:. 84. 



A simple switch provided with a resistance so as to be suited 
to start a motor, is called a motor-starter, and one that in addi- 
tion is provided with means for automatically flying to the open 
position whenever the current fails, is called an automatic under- 
load starter. 

If the motor is very much overloaded, its speed will slow down 
and the current will increase in strength. If the overload is suf- 
ficient, the current will become so strong as to be able to ourn out 

5 



66 



HANDBOOK ON ENGINEERING. 



the armature ; hence, it is desirable to provide a circuit breaker 
that will open the circuit when the current becomes so strong as 
to be liable to burn out the machine. Motor-starters are made 
with a circuit-breaking attachment, and are then called automatic 
overload motor-starters. A device that combines the under and 
overload starter, features is called an automatic under and over- 
load starter, and by some people it is called a " no voltage " and 
" overload starter." 

When motors were first introduced, a great deal of trouble 
was experienced with the starters, owing to the fact that they 
were arranged so that when the motor was stopped, the connection 
with the field coils was broken. Now, the current flowing through 
the field coils objects to stop flowing when the connection is 
broken, and, consequently, it continues to flow between the end of 
switch F in Fig. 84, and the last of the contacts of R, until the 
distance is more than the e.m.f. of the current can overcome. 




Fig. 85. 



This action produces serious sparking at the last terminal, and in 
addition, produces a severe strain upon the insulation of the 



HANDBOOK ON ENGINEERING. 



67 



field coils, because, as the current is headed off in one direction, 
it tries to find an outlet in another. This action is what is 




commonly called the "kick of the motor field." All this 
trouble can be obviated by connecting the starter with the motor 
in such a way that the field circuit is never opened, as is shown 
in Fig. 84. As this is quite an important point, I will present 
it in a more simple form in Fig. 85, in which it will be seen that 
the field coils and armature are permanently connected, so that 
when switch S opens the circuit, the field current can flow through 
the armature, until it dies out. All first-class concerns make 
motor starters with this connection, at the present time. Some 
of them add the curved contact e. Without this contact, it can 
be seen that when the switch S is moved to the top position, the 



68 HANDBOOK ON ENGINEERING. 

resistance R is simply transferred from the armature to the field 
circuit, aud that the current going to the field coils has to pass 
through this resistance. As this resistance is insignificant in 
comparison with that of the shunt coils, it makes little difference 
whether it is left in the field circuit or not, but by the addition of 
e it can be cut out. 

Variable speed motors are always arranged so that the speed 
may be changed by hand as conditions may require. Trolley-car 
motors are of this type, and so are the motors used for printing 
presses, and many other kinds of work. Figs. 86 to 88 show 
arrangements by means of which the speed may be varied with 
series wound motors. In Fig. 86, E is the starting box and i^is 
the speed regulator. " In the act of starting, the switches are in 
the position shown. To start, the switch S and E is turned so 
as to close the circuit with the resistance R all included. S is 
moved toward the left as the armature speeds up, and reaches 
the last position when full speed is attained. If the switch of F 
is now closed, a portion of the current will be diverted from the 
armature, and thus its rotating force will be reduced, and thereby 
its speed. This method of speed control is also arranged so 
that the two switches act together, so as to introduce resistance 
into the motor circuit, and at the same time divert more or less 
of the current around the armature. It is not used extensively, 
as all the current that passes through F is just so much thrown 
away. 

In Fig* 87 the speed is controlled by means of the switch F, 
which cuts out portions of the field coils and this changes the 
strength of the field. With this arrangement, if a portion of 
the field is cut out, the motor will run faster, because the c.e.m.f 
will be reduced, therefore, the armature current will be increased. 
To obtain a wide range of regulation, it is necessary to wind a 
large number of turns of wire on the field, so that with all the 
wire in service, the speed may be the lowest required. 



HANDBOOK ON ENGTNEERINC4. 



69 



Fig"* && shows another arrangement that varies the strength of 
the field by diverting a portion of the current through switch F. 
It gives as wide a range of regulation as Fig. 87, but is not so 
economical. 

Figs- &6 and 88 cannot be used to regulate the speed of shunt 
motors, but Fig. 87 can. The first two named figures, if used 




Fie. 87 



with a shunt motor, would simply afford a third j^ath through 
which current could pass from one side of line to the other, that 
is, from the p to the n wires, but this would not materially affect 
the strength of current that would flow through the armature and 
field coils. They work with series wound motors, because the 
current is not shunted from wire p to wire n but simply from 
one side of the armature, or the field, to the other. 



70 



HANDBOOK ON ENGINEERING. 



Fig* Z9 shows an arrangement by means of which a shunt 
motor can be made for variable speed. In this case, the switch 




Ficr. 88. 



and resistance E is simply an ordinary starter, and F is a resist- 
ance that is introduced in the field circuit, so as to vary the 
strength of the field. With this arrangement the slowest speed is 
obtained when all the resistance of F is out of the circuit. 

The direction in which a motor runs can be reversed by sim- 
ply reversing the direction of the current through the armature. 
Any of the arrangements for varying the speed can be used in 
connection with reversible motors by arranging the switch so as 



HANDBOOK OX ENGINEERING. 



71 



to reverse the armature connections. Fig. 90 will give a fair 
idea of the way in which a reversing switch is made. This repre- 
sents the type of switch used most generally for this purpose, and 
it is known as the cylinder switch. It is the kind used on trol- 
ley-cars. The vertical row of circles numbered . from one to 
eleven represents stationary contact pieces, to which the terminals 
of the motor, the line and the resistance are attached. The 
shaded parts B B are metal plates that are secured to the 
surface of a cylinder, that is so located that as it is turned in one 
direction or the other, these plates slide over the stationary con- 
tacts. If the cylinder is turned so that the plates on the right 
side slide over the contacts, the 'motor will run in one direction, 
and if the cylinder is turned in the other direction, the motor will 
be reversed. Suppose the right side plates slide over the con- 




Fig. 89. 



tacts, then the current f rom p will pass to contact 2, and thence 
to wire a, and to the left-side of the field. Through wire d it 
will return from the field to contact 5, and by means of 



n 



HANDBOOK ON ENGINEERING. 



plates N and T, which are connected as shown at JP, it will reach 
contact 3 and wire 5, which runs to the lower side of the arma- 
ture. From the top of the armature, through wire c, the current 
will return to contact 4 and through plates S and M and the con- 
nection X will reach contact 6, which by one of the wires e con- 




Fig. 90. 



nects with the left-side of the resistance D. From the right-side 
of this resistance, the current will pass to contact 10, and thus 
to contact 11, through the cylinder plate, and in that way reach 
line wire n. 

If the cylinder is turned further around, contact 7 will be cov- 
ered by plate M , and this will cut one section of D. By a further 



HANDBOOK ON ENGINEERING. 73 

movement, contact 8 will be covered, thus cutting out another 
section, and by continuing the movement, all of D can be cut out. 

If the cylinder is turned so as to slide the left- side plates over 
the contacts, the change effected will be that contact 5 will be 
connected with 4 instead of with 3, and contact 6 will be con- 
nected with 3" instead of 4, thus reversing the direction of the 
current through the armature. 

The strength of an electric current is measured in amperes. 
The electromotive force that drives an electric current through a 
circuit is measured in volts. The resistance that a wire or other 
circuit offers to the passage of an electric current through it is 
measured in ohms. 

The unit of resistance, the Ohm, is the resistance of a column 
of mercury about 40 inches long and about five hundredths of an 
inch in diameter, or, to be more exact, 106 centimeters long, and 
one milhmeter in diameter. 

THE WATT. 

The watt is the unit of electric power — the volt ampere, the 
power developed, and is equal to T J ¥ of one horse power. A con- 
venient multiple of this is called the Kilowatt, written K. W., and 
is equal to 1,000 watts. 

THE AHPERE. 

The ampere is the practical unit of electric current, such a cur- 
rent [or rate of flow, or transmission of electricity] as would 
pass, with an electromotive force of one volt, through a circuit 
whose resistance is equal to one ohm ; a current of such a strength 
as would deposit from solution .006084 grains of copper per 

second. 

CANDLE POWER. 

The candle power is the unit of light ; and a standard candle 
is a candle of definite composition which with a given consump- 
tion in a given time, will produce a light of a fixed and definite 
brightness. A candle which burns 120 grains of spermaceti wax 
per hour, or two grains per minute, will give an illumination 
equal to one standard candle. 



74 HANDBOOK ON ENGINEERING. 



CHAPTER VII. 

INSTRUCTIONS FOR INSTALLING AND OPERATING SLOW AND 
MODERATE SPEED GENERATORS AND HOTORS. 

To remove the armature, take off the brush-holders, brush 
yoke, pulley and bearing caps and put a sling on the armature, as 
shown in accompanying illustration. A spreader of suitable 
length should be used and its location adjusted to prevent the 
rope from drawing against the flange or end connections. 

In assembling, marked parts of the machine should be assem- 
bled strictly according to the marking. Clean all connection 
joints carefully before clamping them together. Wipe the shaft- 
bearing sleeves and oil cellars perfectly clean and free from grit. 
Place the bearing sleeves and oil rings in position on the shaft 
and then lower the armature into place, taking care that the oil 
rings are not jammed or sprung. As soon as the armature is in 
position, pour a little oil in the bearing- sleeves, put the caps on 
the boxes and screw them down snugly. The top field should 
next be put on and bolted firmly into position, and a level placed 
on the shaft to check the leveling of the foundation. 

Fill the bearings with the best grade of thin lubricating oil .and 
do not allow it to overflow. Oil throwing is usually due to an 
excess of oil and can be avoided by care in filling the oil cellars. 

To complete the assembly, place the pulley on the shaft, draw 
up the set screws and put on the brush rigging and connection 
blocks. 

STARTING. 

Before putting on the belt, see that all screws and nuts are 
tight and turn the armature by hand to see that it is free and 



HANDBOOK ON ENGINEERING, 75 

does not rub or bind at any point. Put on the belt with the 
machine so placed on the rails as to have the minimum distance 
between pulley centers. Start the machine up slowly and see 
that the oil rings in bearings are in motion. As the machine 




comes up to speed, tighten the belt till it runs smoothly, and run 
the machine long enough without load to make sure that the bear- 
ings are in perfect condition. The bearings, when running, 
should be examined at least once a week. 



CARE OF COMMUTATOR. 

The commutator brushes and brush-holders should at all 
times be kept perfectly clean and free from carbon or other dust. 
Wipe the commutator from time to time with a piece of canvas 
lightly coated with vaseline. Lubricant of any kind should be 
applied very sparingly. 



76 HANDBOOK ON ENGINEERING. 

If a commutator when set up begins to give trouble by rough- 
ness, with attendant sparking and excessive heating, it is neces- 
sary to immediately take measures to smooth the surface. Any 
delay will aggravate the trouble, and eventually cause high tem- 
peratures, throwing off solder, and possibly displacement of the 
segments. No. sandpaper, fitted to a segment of wood, with a 
radius equal to that of the commutator, if applied in time to the 
surface when running at full speed (and if possible with brushes 
raised), and kept moving laterally back and forth on the commu- 
tator, will usually remedy the fault. 



DIRECTIONS FOR STARTING DYNAMOS. 

General. — Make sure that the machine is clean throughout, 
especially the commutator, brushes, electrical connections, etc. 
Remove any metal dust, as it is very likely to make a ground or 
short circuit. 

Examine the entire machine carefully, and see that ~ there are 
no screws or other parts that are loose or out of place. See that 
the oil-cups have a sufficient supply of oil, and that the passages 
for the oil are clean and the feed is at the proper rate. In the 
case of self -oiling bearings, see that the rings or other means for 
carrying the oil work freely. See that the belt is in place and 
has the proper tension. If it is the first time the machine is 
started, it should be turned a few times by hand, or very slowly, 
in order to see if the shaft revolves easily and the belt runs in 
center of pulleys. 

The brushes should now be carefully examined and adjusted 
to make good contact with the commutator and at the proper 
point, the switches connecting the machine to the circuit being 
left open. The machine should then be started with care and 
brought up to full speed, gradually if possible ; and in any case 



HANDBOOK ON ENGINEERING. 77 

the person who starts either a dynamo or a motor should closely 
watch the machine and everything connected with it, and be ready 
to throw it out of circuit if it is connected, and shut down and 
stop it instaDtly if the least thing seems to be wrong, and should 
then be sure to find out and correct the trouble before starting 
again. 

STARTING A DYNAMO. 

In the case of a dynamo it is usually brought up to speed 
either by starting up a steam-engine or by connecting the 
dynamo to a source of power already in motion. The former 
should, of course, only be attempted by a person competent to 
manage steam-engines and familiar with the particular type in 
question. This requires special knowledge acquired by experi- 
ence, as there are many points to appreciate and attend to, the 
neglect of any of which might cause serious trouble. For ex- 
ample, the presence of water in the cylinder might knock out the 
cylinder-head ; the failure to set the feed of the oil-cups properly 
might cause the piston-rod, shaft, or other part, to cut. And 
other great or small damage might be done by ignorance or care- 
lessness. The mere mechanical connecting of a dynamo to a 
source of power is usually not very difficult ; nevertheless, it 
should be done carefully and intelligently, even if it only requires 
throwing in a friction-clutch or shifting a belt from a loose pul- 
ley. To put a belt on a pulley in motion is difficult and danger- 
ous, particularly if the belt is large or the speed is high, and 
should not be tried except by a person who knows just how to do 
it. Even if a stick is used for this purpose, it is apt to be caught 
and thrown around by the machinery, unless it is used in exactly 
the right way. 

It has been customary to bring dynamos to full speed before 
the brushes are lowered into contact with the commutator ; but 



78 HANDBOOK ON ENGINEERING. 

this is not necessary, provided the dynamo is not allowed to turn 
backwards, which sometimes occurs from carelessness in starting, 
and might injure copper brushes by causing them to catch in the 
commutator. If the brushes are put in contact before starting, 
they can be more easily and perfectly adjusted and the e.m.f . 
will come up slowly, so that any fault or difficulty will develop 
gradually and can be corrected ; or the machine can be stopped, 
before any injury is done to it or to the system. In fact, if the 
machine is working alone on a system, and is absolutely free from 
any danger of short-circuiting any other machine or storage bat- 
tery on the same circuit, it may be started while connected to the 
circuit, but not otherwise. If there are a large number of lamps 
connected in the circuit, the field magnetism and voltage might 
not be able to " build up " until the line is disconnected an 
instant. 

If one dynamo is to be connected with another, or to a circuit 
having other dynamos or a storage battery working upon it, the 
greatest care should be taken. This coupling together of 
dynamos can be done perfectly, however, if the correct method is 
followed, but is likely to cause serious trouble if any mistake is 
made. 

SWITCHING DYNAHOS INTO CIRCUIT. 

Two or more machines are often connected to a common cir- 
cuit. This is especially the case in large buildings where the 
number of lamps required to be fed varies so much that one 
dynamo may be sufficient for certain hours, but two, three or 
more machines may be required at other times. The various 
ways in which this is done depending upon the character of the 
machines and of the circuit and the precautions necessary in 
each case make this a most important and interesting subject, 
which requires careful consideration. 

Dynamos may be connected together either in parallel (mul- 
tiple arc) or in series. 



HANDBOOK ON ENGINEERING. 79 



DYNAMOS IN PARALLEL. 

In this case the + terminals are connected together or to the 
same line, and the — terminals are connected together or to the 
other line. The currents (i. e. amperes) of the machines are 
thereby added, but the e.m.f. (volts) are not increased. The 
chief condition for the running of dynamos in parallel is that 
$heir voltages shall be equal, but their current capacities may be 
different. For example : A dynamo producing 10 amperes may 
be connected to another generating 100 amperes, provided the 
voltages agree. Parallel working is, therefore, suited to constant 
potential circuits. A dynamo to be connected in parallel with 
others or with a storage battery, must first be brought up to its 
proper speed, e.m.f., and other working conditions, otherwise, 
it will short-circuit the system, and probably burn out its 
armature. Its field magnetism must, therefore, be at full 
strength, owing to the fact that it generates no e.m.f. with 
no field magnetism. Hence, it is well to find whether the pole 
pieces are strongly magnetized by testing them with a piece of 
iron, and to make sure of the proper working of the machine in 
all other respects before connecting the armature to the circuit. 
It is a common accident for the field-circuit to be open at some 
point, and thus cause very serious results. In fact, a dynamo 
should not be connected to a circuit in parallel with others until 
its voltage has been tested and found to be equal to, or slightly 
(not over 1 or 2 per cent) greater than that of the circuit. If the 
voltage of the dynamo is less than that of the circuit, the current 
will flow back into the dynamo and cause it to be run as a motor. 
The direction of rotation is the same, however, if it is shunt- 
wound, and no great harm results from a slight difference of 
potential. But a compound-wound machine requires more careful 
handling. 



80 HANDBOOK ON ENGINEERING. 



DIRECTIONS FOR RUNNING DYNAMOS AND MOTORS. 

In the case of a machine which has not been run before, or 
has been changed in any way, it is of course wise to watch it 
closely at first. It is also well to give the bearings of a new 
machine plenty of oil at first, but not enough to run on the arma- 
ture, commutator or any part that would be injured by it, and 
to run the belt rather slack until the bearings and belt have got- 
ten into easy working condition. If possible a new machine 
should be run without load or with a light one for an hour or 
two, or several hours in the case of a large machine ; and it is 
always wrong to start a new machine with its full load, or even a 
large fraction of it. *" 

This is true even if the machine has been fully tested by its 
manufacturer and is in perfect condition, because there may be 
some fault in setting it up, or some other circumstance which 
would cause trouble. All machinery requires some adjust- 
ment and care for a certain time to get it into smooth working 
order. 

When this condition is reached, the only attention required 
is to supply oil when needed, keep the machine clean and see 
that it is not overloaded. A dynamo requires that its voltage or 
current should be observed and regulated if it varies. The per- 
son in charge should always be ready and sure to detect the 
beginning of any trouble, such as sparking, the heating of any 
part of the machine, noise, abnormally high or low speed, etc. ; 
before any injury is caused, and to overcome it by following 
directions given elsewhere. Those directions should be pretty 
thoroughly committed to mind, in order to facilitate the prompt 
detection and remedy of any trouble when it suddenly occurs, as 
is apt to be the case. If possible, the machine should be shut 



HANDBOOK ON ENGINEERING. 81 

down instantly when any trouble or indication of one appears, in 
order to avoid injury and give time for examination. 

Keep all tools or pieces of iron or steel away from the machine 
while running, as they might be drawn in by the- magnetism, and 
perhaps get between the armature and pole-pieces and ruin the 
machine. For this reason, use a zinc, brass or copper oil-can 
instead of iron or " tin " (tinned iron). 

Particular attention and care should be given to the commu- 
tator and brushes to see that the former keeps perfectly smooth 
and that the latter are in proper adjustment. (See Sparking.) 

Never lift a brush while the machine is delivering current, 
unless there are one or more other brushes on the same side to 
carry the current, as the spark might make a bad burnt spot on 
the commutator. 

Touch the bearing's and field-coils occasionally to see that 
they are not hot. To determine whether the armature is running 
hot, place the hand in the current of air thrown out from it by 
centrifugal force. 

Special care should be observed by any one who runs a dynamo 
or motor to avoid overloading it, because this is the cause of most 
of the troubles which occur. 

6 



82 HANDBOOK ON ENGINEERING. 



CHAPTER VIII. 

WHY COMMUTATOR BRUSHES SPARK AND WHY THEY DO 
NOT SPARK. 

I might give a long list of reasons why commutator brushes 
spark, and why they do not spark, but by such a procedure no 
light would be thrown on the subject, because the reasons would 
not be understood unless fully explained. I therefore propose to 
explain the subject and let the reader tabulate the reasons after 
digesting the explanation of the principles involved. 

Whenever an electric current is interrupted, a spark is pro- 
duced and it makes no difference how the current is generated, 
or what kind of a conductor it is flowing through. To break 
a current without a spark is not a possibility; hence, if we 
desire to open a circuit without producing a spark, the only way 
to accomplish the result is by killing the current before the 
circuit is opened. The brushes resting on the commutator of a 
motor or a generator have to transmit to the armature and take 
away from it the current that is generated, in the case of a 
generator, or the current that drives the machine in the case of a 
motor. If the brushes were made so narrow that they could only 
make contact with one commutator segment at a time, it would 
be impossible to run the machine without producing very destruc- 
tive sparks. Commutators, however, are not made in this way. 
The insulation between the segments is narrow, and the brushes 
are wide enough to be always in contact with two segments, and 
part of the time with three. Suppose that the proportions are 
such that during most of the time the brush only touches two 




HANDBOOK ON ENGINEERING. 83 

segments, as shown in Fig. 1. With these proportions it will be 
seen, that so long as there are two segments in contact with each 
brush, it is a possibility *or the current to be diverted through 
one of them only. Suppose that at the instant when the forward 
segment is passing from under the brush, all the current flows 
through the rear segment ; then it is quite evident that the first- 
named segment will break away from contact with the brush with- 
out making a spark, for there will be no current flowing from it 
to the brush. 

All the foregoing is self-evident, but it will be suggested that 
although the brush can break away from the front segment with- 
out producing a spark, it cannot do the same thing with the rear 
segment, for all the current is flowing through this one. While 
it is true that when the forward segment passed from under the 
brush all the current was flowing through the rear segment, it is 
not true that the current continues to follow this path. As soon 
as the front segment passes from under the brush, the rear one 
becomes the forward segment, and while it is advancing to the 
point where it must pass from under the brush, the current can 
be transferred to the next segment back of it which now plays 
the part of rear segment. Thus we see that to be able to run a 
machine without producing sparks at the commutator, all we have 
to do is to provide means whereby the current is transferred from 
one segment to the one back of it as the commutator revolves, so 
that when the segments pass from under the brush there is no 
current flowing through them, This result is accomplished more 
or less perfectly in all machines, made by responsible firms. 
There are machines on the market that have been designed by 
men that are not well enough posted in the principles of electrical 
science to obtain proper proportions, and these are not propor- 
tioned so as to shift the current from the forward to the rear 
segment as fast as the machine revolves ; such machines always 
produce more or less serious sparking. 



84 HANDBOOK ON ENGINEERING. 

If a machine is accurately made and the armature coils and 
commutator segments are properly spaced and sufficient in num- 
ber, it is possible to get the brushes so there will be little or no 
spark at a given load ; but if the current strength be increased or 
reduced, the sparks will appear, and the more the current is 
changed the larger the sparks will be, the increasing current 
producing the greatest sparking. 

The way in which the current is shifted from the front to the 
rear segment I will explain in connection with Fig. 1. In this 
figure, -4 .represents a portion of the core of a ring armature. 
The shaft upon which it is mounted is shown at D, and P N are 
the corners of the poles between which it rotates. The small 
blocks C represent a portion of the commutator segments, which 
we have placed outside of the armature, so as to make the diagram 
as simple as possible. For the same reason I have shown the 
armature coils as made of two turns of wire each. The line F 
divides the space between the ends of the poles into two equal 
parts, and the line E divides the armature into two halves 
on which the directions of the induced currents is opposite. In 
all the coils to the right of line E the currents are induced in 
a direction away from the shaft, and in all the coils to the left 
of line E the currents flow toward the shaft, all of which is 
clearly indicated by the arrow heads placed upon the lines repre- 
senting the coils. The outline B represents the end of one of the 
brushes, and from the direction in which it is inclined it will be 
understood that the armature revolves in a direction counter to 
that of the hands of a clock. 

When the armature is in the position shown, the current flow- 
ing in the coils to the right of line E passes to segments, and 
thus reaches the brush, while the current flowing in the coils 
to the left of line E reaches segment a, and through this passes 
to the brush. As the brush rests upon segments a and b the 
coil with which they connect is short-circuited, and therefore a 



HANDBOOK ON ENGINEERING. 



85 



current can flow in it in any direction, or there may be no cur- 
rent. To be able to run without spark, or to obtain perfect 
commutation, as it is called, the current in this short-circuited 
coil, when in the position shown, should be zero, or nearly so. 
This coil, which is short-circuited by the brush, is called the com- 
mutated coil, or the coil undergoing commutation. It will be 
noticed that this commutated coil is in a position just forward of 




Fig. 1. 

the line E ; hence, the action of pole P will be to develop a 
current in it that will flow in the same direction as the current 
in the coils ahead of it, that is, in the coils to the left. Now if 
this current flowed through the brush, it would be in a direction 
contrary to that of the arrow at a; hence it would act to check 
the current flowing from the front segment a to the brush, and 
would divert it through the commutated coil to the rear segment 



86 HANDBOOK ON ENGINEERING. 

b. If the action of pole P upon the commutated coil is sufficiently 
vigorous, the current developed in it will be as strong as the cur- 
rent in the coils ahead of it, by the time the end of the segment 
is about to break away from the brush ; and this being the case 
there will be no current from segment a to the brush, and conse- 
quently, no spark. If the action of pole P is not strong enough, 
then there will be a small current from segment a to the brush 
when they separate, and as a result, a small spark. If the action 
of pole P on the commutated coil is too vigorous, then the current 
developed in it will be too great, and it will not only divert all 
the current coming from the forward coils, through the commuta- 
ted coil to segment 6, but in addition will develop a local current 
that will circulate through the end of the brush, and, therefore, 
when the separation occurs, there will be a current flowing from 
the brush to the front segment, and consequently a spark. 

If the commutated coil were placed astride of line E, the 
action of pole P upon it would be no greater than that of pole JV, so 
that no current would be developed in it while undergoing com- 
mutation. The further the coil is in advance of line E, when short- 
circuited by the brash, the stronger the action of pole P upon it ; 
therefore, the strength of the current developed in the commutated 
coil can be increased by moving the brush further away from pole P. 
Hence, by trial, a point can be found where the current developed 
will be just sufficient for the purpose and no more. This is true, 
supposing the current developed by the armature to remain con- 
stant, but, if it varies, the current in the commutated coil will be 
either too great or too small. If, when the brushes are set, the 
armature is delivering a current of, say, twenty amperes, then the 
current flowing through the coils to the left of the brush will be 
ten amperes, and the current in the commutated coil will also be 
ten amperes. If the armature current increases to forty amperes, 
the current in the forward coils will be twenty amjDeres, and as that 
•n the commutated 'coils will still be ten amperes, it will have only 



HANDBOOK ON ENGINEERING. 87 

one-half the strength required for perfect commutation. In prac- 
tice, however, it is found that if the commutator have a sufficient 
number of segments, and the proportions of the machine are such 
that the line E remains practically in the same position for all 
strengths of armature current, then, if the brushes are set so as to 
run sparkless with an average load, they will run so nearly spark- 
less with a heavy or light load as to make it difficult to detect the 
difference. 

Even when a machine is properly proportioned, the brushes 
may spark badly if they are not set in the proper position and 
with the proper tension. If the tension is not right, they will 
spark no matter where they are set. If the tension is too light, 
they will spark, because they will chatter and thus jump off the 
surface of the commutator. If the tension is too great, they will 
spark because they will cut the commutator, and then the latter 
will act as a file or grindstone and cut away particles from the 
brushes, and these will conduct the current from segment to seg- 
ment, as well as from the segment to the brush. Whenever a com- 
mutator is seen to be covered with fine sparks, some of which run 
all the way around the circle, it may be depended upon that the 
surface is rough, due in most cases to too much pressure on the 
brushes, and the remedy is to smooth it up and reduce the tension 
and set the brushes where they will run with the smallest spark. 
When the brushes begin to spark they rarely cure themselves and 
the longer they are allowed to run with a heavy spark the worse 
they will get. 

Of all the troubles which may occur, sparking is the only one 
which is very different in the different types of machines. In 
some its occurrence is practically impossible. In others, it may 
result from a number of causes. The following cases of sparking 
apply to nearly all machines, and they cover closed-coil dynamos 
and motors completely. 

Cause \* — Brushes not set at the neutral point. 



88 HANDBOOK ON ENGINEERING. 

Symptom, — Sparking, varied by shifting the brushes with 
rocker-arm. 

Remedy* — Carefully shift brushes backwards or forwards 
until sparking is reduced to a minimum. 

The usual position for" brushes in two-pole mrchines is 
opposite the "spaces between the pole-pieces. 

Cause 2* — Commutator rough, eccentric, or has one or more 
" high bars " projecting beyond the others, or one or more flat 
bars, commonly called " flats," or projecting mica, any one of 
which causes brush to vibrate, or to be actually thrown out of 
contact with commutator. 

Symptom* — Note whether there is a glaze or polish on the 
commutator, which shows smooth working ; touch revolving com- 
mutator with tip of finger-nail, and the least roughness is 
perceptible, or feel of brushes to see if there is any jar. If the 
machine runs at high- voltage (over 250), the commutator or 
brushes should be touched with a small stick or quill to avoid 
danger of shock. In the case of an eccentric commutator, careful 
examination shows a rise and fall of the brush when commutator 
turns slowly, or a chattering of brush when running fast. 

Remedy* — Smooth the commutator with a fine file or fine sand- 
paper, which should be applied by a block of wood which exactly 
fits the commutator (in latter case, be careful to remove any sand 
remaining afterward ; and never use emery') . If bearing is loose 
put in new one. If commutator is very rough or eccentric, it 
should be taken out and turned off. 

Cause 3* — Brushes make poor contact with commutator, 

Symptom* — Close examination shows that brushes touch only 
at one corner, or only in front or behind, or there is dirt on sur- 
face of contact. Sometimes, owing to the presence of too much 
oil or from other cause, the brushes and commutator become very 
dirty and covered with smut. They should then be carefully 
cleaned by wiping with oily rag or benzine, or by other means. 



HANDBOOK ON ENGINEERING. 89 

Occasionally a " glass-hard " carbon brush is met with. It 
is incapable of wearing to a good seat or contact and will only 
touch in one or two points, and should be discarded. 

Remedy* — File, bend, adjust or clean brushes until they rest 
evenly on commutator, with considerable surface of contact and 
with sure but light pressure. 

It sometimes happens that the brushes make poor contact, 
because the brush-holders do not turn or work freely. 

Cause 4* — Short-circuited coil in armature or reversed coil. 

Symptom* — A motor will draw excessive current, even when 
running free without load. A dynamo will require considerable 
power even without any load. 

The short-circuited coil is heated much more than the others, 
and is very apt to be burnt out entirely ; therefore, stop machine 
immediately. If necessary to run machine to locate the short- 
circuit, one or two minutes is long enough, but it may be re- 
peated until the short-circuited coil is found by feeling the arma- 
ture all over. 

An iron screw-driver or other tool held between the field- 
magnets near the revolving armature vibrates very perceptibly 
as the short-circuited coil passes. Almost any armature, par- 
ticularly one with teeth, will cause a slight but rapid vibration of 
a piece of iron held near it, but a short-circuit produces a 
much stronger effect only once per revolution. 

The current pulsates and torque is unequal at different parts 
of a revolution, these being particularly noticeable when arma- 
ture turns rather slowly. If a large portion of the armature is 
short-circuited, the heating is distributed and harder to locate. 
In this case a motor runs very slowly, giving little power, but 
having full-field magnetism. 

Remedy* — A short circuit is often caused by a piece of solder 
or other metal getting between the commutator bars or their con- 
nections with the armature, and sometimes the insulation between 



90 HANDBOOK ON ENGINEERING. 

or at the ends of these bars is bridged over by a particle of metal. 
In any such case the trouble is easily found and corrected. If, 
however, the short-circuit is in the coil itself, the only real cure is 
to rewind the coil. 

One or more ' ' grounds ' ' in the armature may produce effects 
similar to those arising from a short circuit. 

Cause 5. — Broken circuit in armature. 

Symptom* — Commutator flashes violently while running, and 
commutator-bar nearest the break is badly cut and burnt ; but in 
this case no particular armature coil will be heated, as in the last 
case and the flashing will be very much worse, even when turn- 
ing slowly. This trouble, which might also be confounded 
with a bad case of " high-bar" or eccentricity in commutator 
(sparking), is distinguished from it by slowly turning the arma- 
ture, when violent flashing will continue if circuit is broken, 
but not with eccentric commutator or even with " high bar." 

Remedy* — The trouble is often found where the armature 
wires connect with the commutator and not in the coil itself, and 
the break may be repaired or the loose wire may be resoldered or 
screwed back in place. If the trouble is due to a broken com- 
mutator connection and it cannot be fixed, then connect the dis- 
connected bar to the next by solder, or " stagger " the brushes ; 
that is, put one a little forward and the other back so as to bridge 
over the break. If the break is in the coil itself, rewinding is 
generally the only cure. 

Cause 6. — Weak field-magnetism. 

Symptom* — Any considerable vibration is almost sure to pro- 
duce sparking, of which it is a common cause. This sparking 
may be reduced by increasing the pressure of the brushes on the 
commutator, but the vibration itself should be overcome by the 
remedies referred to above. 

Cause 7. — Chatter of Brushes. The commutator sometimes 



HANDBOOK ON ENGINEERING. 91 

becomes sticky when carbon brushes are used, causing friction, 
which throws the brushes into rapid vibration as the commutator 
revolves, similarly to the action of a violin-bow. 

Symptom, — Slight tingling or jarring is felt in brushes. 

Remedy. — Clean commutator and oil slightly. This stops it 
at once. 

NOISE. 

Cause 8. — Vibration due to armature or pulley being out of 
balance. 

Symptom* — Strong vibration felt when the hand is placed 
upon the machine while it is running. Vibration changes greatly 
if speed is changed. 

Remedy* — The easiest method of finding in which direction 
the armature is out of balance is to take it out and rest the shaft 
on two parallel and horizontal A-shaped metallic tracks suffici- 
ently far apart to allow the armature to go between them. If the 
armature is then slowly rolled back and forth, the heavy side will 
tend to turn downward. The armature and pulley should always 
be balanced separately. An excess of weight on one side of the 
pulley and an equal excess of weight on the opposite side of the 
armature will not produce a balance while running, though it 
does when standing still ; on the contrary, it will give the shaft 
a strong tendency to "wobble." A perfect balance is only 
obtained when the weights are directly opposite, i. e., in the 
same line perpendicular to the shaft. 

Cause 9* — Armature strikes or rubs against pole pieces. 

Symptom. — Easily detected by placing the ear near the pole- 
pieces, or by examining armature to see if its surface is abraded 
at any point, or by examining each part of the space between 
armature and field, as armature is slowly revolved, to see if any 



92 HANDBOOK ON ENGINEERING. 

portion of it touches or is so close as to be likely to touch when 
the machine is running. Or turn armature by hand when no 
current is on, and note if it sticks at any point. 

Remedy. — Bind down any wire, or other part of the armature 
that may project abnormally, or file out the pole-pieces where the 
armature strikes, or center the armature so that there is a uni" 
form clearance between it and the pole-pieces at all points. 

Cause JO* — Singing or hissing of brushes. This is usually 
occasioned by rough or sticky commutator, or by tips of brushes 
not being smooth, or the layers of a copper brush not being held 
together and in place. With carbon brushes, hissing will be caused 
by the use of carbon which is gritt}^ or too hard. Vertical carbon 
brushes, or brushes inclined against the direction of rotation, are 
apt to squeak or sing. A new machine will sometimes make 
noise from rough commutator, no matter how carefully it is 
turned off, because the difference in hardness between mica and 
copper causes the cut of the tool to vary, thus forming inequali- 
ties which are very minute, but enough to make noise. This 
can be best smoothed by running. 

Remedy* — Apply a ver V little oil or vaseline to the com- 
mutator with the finger or a rag. Adjust the brushes or smooth 
the commutator. Carbon brushes are apt to squeak in starting 
up, or at slow speed. This decreases at full speed, and can 
usually be reduced by moistening the brush with oil, care being 
taken not to have a ay drops, or excess of oil. Shortening or 
lengthening the brushes sometimes stops the noise. Run the 
machine on open circuit until commutator and brushes are 
worn smooth. 



HANDBOOK ON ENGINEERING. 93 



HEATING IN DYNAHO OR MOTOR. 

General Instructions* — The degree of heat that is injurious or 
objectionable in any part of a dynamo or motor is easily deter- 
mined by feeling the various parts. If the heat is bearable for a 
few moments, it is entirely harmless. But if the heat is unbear- 
able for more than a few seconds, the safe limit of temperature 
has been passed, except in the case of commutators in which 
solder is not used ; and it should be reduced in some of the ways 
that are given above. In testing with the hand, allowance should 
always be made for the fact that bare metal feels much hotter 
than cotton, etc. If the heat has become so great as to produce 
an odor or smoke, the safe limit has been far exceeded and the 
current should be shut off and the machine stopped immediately, 
as this indicates a serious trouble, such as a short-circuited coil or 
a tight bearing. The machine should not again be started until 
the cause of the trouble has been found and positively overcome. 
Of course neither water nor ice should ever be used to cool elec- 
trical machinery, except possibly the bearings of large machines, 
where it can be applied without danger of wetting the other 
parts. 

Feeling for heat will answer in ordinary cases, but of course, 
the sensitiveness of the hand differs, and it makes a very great 
difference whether the surface is a good or bad conductor of heat. 
The back of the hand is more sensitive and less variable than the 
palm for this test. But for accurate results a thermometer 
should be applied and covered with waste or cloth to keep in 
the heat. In proper working the temperature of no parts of 
the machine should rise more than 45° C, or 81° F. above the tem- 
perature of the surrounding air. If the actual temperature of 



94 HANDBOOK ON ENGINEERING. 

the machine is near the boiling point, 100° C, or 212° F., it is 
seriously high. 

It is very important in all cases of heating to locate correctly 
the source of heat in the exact part in which it is produced. It 
is a common mistake to suppose that any part of a machine which 
is found to be hot is the seat of the trouble. A hot bearing may 
cause the armature or commutator to heat or vice versa. In 
every case, all parts of the machine should be felt to find which 
is the hottest, since heat generated in one part is rapidly diffused 
throughout the entire machine. It is generally much surer and 
easier in the end to make observations for heating by starting 
with the whole machine perfectly cool, which is done by letting it 
stand for one or more hours or over night, before making the 
examination, When ready to try it, run it fast for three to five 
minutes, with the field magnets charged ; then stop, and feel all 
parts immediately. The heat will be found in the right place, as 
it will not have had time to diffuse from the heated to the cool 
parts of the machine. Whereas, after the machine has run some 
time, any heating effect will spread until all parts are equal in 
temperature, and it will then be almost impossible to locate the 
trouble. 

Excessive heating of commutator, armature, field magnets, or 
bearings may occur in any type of dynamo or motor, but it can 
almost always be avoided by proper care and working conditions. 



THE EFFECT OF THE DISPLACEHENT OF THE ARMATURE. 

If a machine is old, it is more than likely the shaft will be 
found out of center, and if this fact is discovered at a time when 
things are not working as they should, it is taken for granted this 
is the cause of the trouble. What is true of shafts out of the 



HANDBOOK ON ENGINEERING. 



95 



center is true of several other things that are liable to get out of 
place. For the present it will be sufficient to investigate just 
what effect the displacement of the shaft can have. 

Fig* i illustrates an armature of a two-pole machine which is 
out of center in one direction, and Fig. 2 shows another two-pole 
armature out of center in a direction of right angles to that 
shown in the first figure. The condition shown in Fig. 1 could 
be produced by a heavy armature running in rather light bear- 
ings for several years, and the side displacement of Fig. 2 could 
be produced by the tension of an extra tight belt. The mechan- 




Fig. 1 



ical effect of both these conditions would be to increase the pres- 
sure on the bearings, as the part a of the armature would be 
drawn toward the poles of the field with greater force than the 
opposite side. The downward pull, due to the attraction of the 
magnetism, would be greater in Fig. 1 than the side pull in Fig. 
2, supposing both armatures and fields to be the same in both 
cases, and the displacement of the shafts equal. This difference 
is due to the fact that in Fig. 1 the magnetism of both poles is 
concentrated at the lower corners on account of the shorter air 
gap ; hence both sides pull much harder on the lower side. In 



96 HANDBOOK ON ENGINEERING. 

Fig. 2 the pull of the N pole is greater than that of the other, 
simply because in the latter the magnetism is more dispersed, but 
the difference in the density on the two sides will not be very 
great. If the bearings of a machine, with the armature dis- 
placed, as indicated, have shown any signs of cutting, or if they 
run unusually warm, their condition will be improved by putting 
in new bearings that will bring the sfoaft central. 

If the armature is of the drum type, the displacement of the 
shaft will have no effect upon it electrically. This is owing to the 
fact that all the armature coih are wound from one side of 
the core to the other, and, therefore, at all times, every 
coil has one side under the influence of one pole and the other 
side under the influence of the opposite pole, and if one 
side is acted upon strongly by one pole, it will be acted 
upon feebly by the other. If the armature is of the ring type, 
then the displacement of the shaft will affect it electrically, for 
in a ring armature, the coils on one side are acted upon by 
the pole on that side, only, and as the magnetic field from one 
pole will be stronger than that from the other (that is, considering 
the action upon equal halves of the armature) , the voltage devel- 
oped in the coils on one side of the armature will be greater than 
that developed on the other side. 

The effect of the disturbance of the electrical balance will be 
that the brushes will spark badly, because the voltage of the cur- 
rent generated on one side of the armature will be greater than 
that of the current on the other side. Hence, when these two 
currents meet at the brushes, the strong one will tend to drive 
the weak one backward. If, while the armature is out of center, 
we wish to adjust the brushes so as to get rid of the excessive 
sparking, all we have to do is to set them to the right of the cen- 
ter line, as in Fig. 2, so that the wire on the left side will cover a 
greater portion of the circumference than the right. 



HANDBOOK ON ENGINEERING. 97 

In a multipolar machine, the displacement of the armature 
will have the same effect mechanically as in the two-pole type ; 
multipolar armatures are connected in two different ways, one of 
which is called the wave or series winding, and the other the lap 
or parallel winding, In the first named type of winding, the 
ends of all the coils on the armature are connected with each 
other and with the commutator segments in such, a manner that 
there are only two paths through the wire for the current ; there- 
fore, these two armature currents pass under all the poles and 
the voltage of each current is the combined effect of all the poles. 
From this very fact, it can be clearly seen that it makes no 
difference what the distance between the several poles and arma- 
ture may be, for if some are nearer than the others, the only 
effect will be that these poles will not develop their share of the 
total voltage, but whatever their action may be, it will be the 
same on the coils in both circuits. 

When a multipolar armature is connected so as to form a 
parallel or lap winding, then the connections between the coil 
ends, and between these ends and the commutator segments, are 
such that as many paths are provided for the current as there are 
poles, and each one of these paths is located under one pole, and 
as a consequence, the voltage developed in it is proportional to 
the action of this pole. The diagram 3 illustrates a six-pole 
armature with the ends of the field poles, and the arrows aa,bb, 
c c, indicate the six separate divisions of the coils in which the 
branch currents are developed. Now, it can be clearly seen that 
as the armature is nearer to the lower poles than to any of the 
others, the action of these will be the strongest. Hence, the cur- 
rents a a will be stronger than the others and will have a higher 
voltage. 

The two upper currents are weaker than the side ones and 
7 



98 



HANDBOOK ON ENGINEERING. 



their voltage is also lower, so that, the current returning to the 
commutator through the brushes at the upper corners, will not 
divide equally, but the larger portion will be drawn into the coils 
on the side ; and as the upper coils will have to fight to hold their 
own, so to speak, there will be a disturbance of the balance that 




Fig. 3. 



is required for smooth running. The result will be heavy spark- 
ing at these brushes. In the great majority of cases, if the brushes 
of a multipolar machine spark on account of the armature being 
out of center, the only cure is to reset the bearings, if they are 
adjustable, and if they are not, to put in new ones. 



HANDBOOK ON ENGINEERING, 



99 



Table of Carrying Capacity of Wires. — Below is a table which 
must be followed in placing interior conductors, showing the 
allowable carrying capacity of wires and cables of ninety-eight 
per cent conductivity, according to the standard adopted by the 
American Institute of Electrical Engineers. 





Table A. 


Table B. 






Rubber-Covered 


Weatherproof 






Wires, 


Wires. 




B. & S. G. 


Amperes. 


Amperes. 


Circular Mill 


18 


3 


5 


1,624 


16 


6 


8 


2,583 


14 


12 


16 


4,107 


12 


17 


23 


6,530 


10 


24 


32 


10,380 


8 


33 


46 


16,510 


6 


46 


65 


26,250 


5 


54 


77 


33,100 


4 


65 


92 


41,740 


3 


76 


110 


52,630 


2 


90 


131 


66,370 


1 


107 


156 


83,690 





127 


185 


105,500 


00 


150 


220 


133,100 


000 


177 


262 


167,800 


0000 


210 


312 


211,600 


Circular Mills. 








200,000 


200 


300 




300,000 


270 


400 




400,000 


330 


500 




500,000 


390 


590 




•600,000 


450 


680 




700,000 


500 


760 




800,000 


550 


840 




900,000 


600 


920 


4 



100 HANDBOOK ON ENGINEERING. 





Table a. 


Table v>. 




RuM>er-Covere< 


Weatherproof 




Wires. 


Wires. 


Circular Mills. 


Amperes. 


Aropi 


1,000,000 


(550 


1,000 


1,100,000 


600 


1,080 


1,200,000 


730 


1,150 


1,300,000 


770 


1,220 


1,400,000 


810 


1,290 


1,500,000 


850 


1,360 


1,600,000 


890 


1,430 


1,700,000 


940 


1,490 


1,800,000 


970 


1,550 * 


1,900,000 


1,010 


1,610 


2,000,000 


1,050 


1,670 



The lower limit is specified for rubber-covered wires to pre- 
vent gradual deterioration of the high insulations by the heat 
of the wires, but not from fear of igniting the insulation. The 
question of drop is not taken into consideration in the above 
tables. 

Insulation Resistance. — The wiring in any public building 
must test free from grounds ; i. e., the complete installation must 
have an insulation between conductors and between all conduc- 
tors and the ground (not including attachments, sockets, recep- 
tacles, etc.) of not less than the following: — ■ 

Up to -5 amperes, 4,000,000 Up to 
" 10 " 2,000,000 

« 25 " 800,000 

" 50 " 400,000 tl 

" 100 " 200,000 

All cutouts and safety devices in place in the above. 
Where lamp sockets, receptacles and electroliers, etc., are con- 
nected, one-half of the above will be required. 



200 


amperes j 


100,000 


400 


" 


25,000 


800 


" 


25,000 


1,600 


" 


12,500 



HANDBOOK ON ENGINEERING. 



101 



Soldering Fluid. — a. The following formula for soldering 
fluid is suggested : — 

Saturated solution of zinc chloride, 5 parts. 
Alcohol, 4 parts. 

Glycerine, 1 part. 

Bell or Other Wires. — a. Shall never be run in same duct 
with lighting or power wires. 

Table of Capacity of Wires. — 



6 

w 
« 

19 


go 

< 

1,288 


a 

co 
o 
d 


go 

CO CO 

o 

CO 


a 


18 


1,624 






3 


17 


2,048 








16 


2,583 






6 


15 


3,257 








14 


4,107 






12 


12 


6,530 






17 




9,016 


7 


19 


21 




11,368 


7 


18 


25 




14,336 


7 


17 


30 




18,081 


7 


16 


35 




22,799 


7 


15 


40 




30,856 


19 


18 


50 




38,912 


19 


17 


60 




49,077 


19 


16 


70 




60,088 


37 


18 


85 




75,776 


37 


17 


100 




99,064 


61 


18 


120 




124,928 


61 


17 


145 


... 


157,563 


61 


16 


170 



102 



HANDBOOK ON ENGINEERING. 



O 


op. 


o 


33 


61 


15 


61 


14 


91 


15 


91 


14 


127 


15 



198,677 61 15 200 

250,527 61 14 235 

296,387 91 15 270 

373,737 91 14 320 

413,639 127 15 340 

When greater conducting area than that of B. & 8. G. is re- 
quired, the conductor shall be stranded in a series of 7, 19, 37, 
61, 91 or 127 wires, as may be required; the strand consisting 
of one central wire, the remainder laid around it concentrically, 
each layer to be twisted in the opposite direction from the pre- 
ceding. 

TABLE SHOWING THE SIZE OF WIRE OF DIFFERENT METALS THAT 
WILL BE MELTED BY CURRENTS OF VARIOUS STRENGTHS. 



Strength 


DIAMETER OP 


WlRE IN THOUSANDTHS OF AN INCH. 
















in 
Amperes. 


Copper. 


Aluminum. 


Platinum. 


German 

Silver. 


Iron. 


Tin. 


1 


.002 


.003 


.003 


.003 


.005 


.007 


2 


.003 


.004 


.005 


.005 


.008 


.011 


3 


.004 


.005 


.007 


.007 


.010 


.015 


4 


.005 


.006 


.008 


.008 


.012 


.018 


5 


.006 


.008 


.010 


.010 


.014 


.021 


10 


.009 


.012 


.016 


.016 


.022 


.033 


15 


.013 


.016 


.020 


.020 


.028 


.044 


20 


.015 


.019 


.025 


.025 


.034 


.053 


25 


.018 


.022 


.029 


.029 


.040 


.062 


30 


.020 


.025 


.032 


.032 


.045 


.069 


35 


.022 


.028 


.036 


.036 


.050 


.077 


40 


.025 


.030 


.039 


.039 


.055 


.084 


50 


.027 


.033 


.042 


.042 


.059 


.091 


60 


.029 


.035 


.045 


.045 


.063 


.098 



HANDBOOK ON ENGINEERING. 103 



CHAPTER IX. 

INSTRUCTIONS FOR INSTALLING AND OPERATING APPAR- 
ATUS FOR ARC LIGHTING, BRUSH SYSTEM. 

Theory of the Brush arc generator. — The Brush Arc Gen- 
erator is of the open coil type, the fundamental principle of which 
is illustrated in Fig. 1. Two pairs of coils, placed at right angles 




Fig. i, 

on an iron core, are rotated in a magnetic field. The horizontal 
coils represented in the diagram are producing their maximum 
electromotive force, while the pair of coils at right angles to them 
is generating practically no electromotive force. The brushes 
are placed on the segments of the four-part commutator, so as to 
collect only the current generated by the two horizontal coils. 
The other coils are open circuited, or completely cut out of the 
circuit. 



104 HANDBOOK ON ENGINEERING. 

Such a machine will generate current, continuous in direction, 
-but fluctuating considerably in amount. These fluctuations will 
be diminished by the addition of more coils to the armature. 




Fig, 2 is a diagrammatic representation of an eight coil 
machine. The ends of coils diametrically opposite are connected 
as in the four-pole machine, but to avoid complications, these 
connections have been omitted on the diagram. In the eight coil 
machine, one pair of coils, A 1 , A 2 , is generating maximum elec- 
tromotive force. At right angles to these coils, the coils C 1 and 
C 2 are generating no electromotive force. In intermediate 
positions, the coils B 1 , IP, D 1 , D 2 are generating a useful electro- 
motive force, although one which is not so high as that generated 
by the coils A 1 and A 2 . 

In collecting 1 the. current from such an armature, the coils in 
the intermediate positions cannot be connected in parallel with 
the coils generating maximum electromotive force, because their 
electromotive force is lower. The pair of coils A 1 , A 2 can, how- 
ever, be placed in series and connected in series with the two pairs 



HANDBOOK ON ENGINEERING. 



105 



of coils B 1 , B 2 and D 1 , D 2 , which may be placed in parallel with 
each other, since they occupy similar positions in the magnetic fledl. 

In the Brush Arc Generator a double commutator is used to 
automatically make these connections. 

In Fig* 3 this commutator is developed or spread out, and the 
coils are represented diagrammatically. 




Fig. 3. 



BIPOLAR BRUSH ARC GENERATORS. 

Bipolar Brush Machines were, built in eight sizes, ranging 
in capacity from 1 to 65 lamps of 2000 candle-power, and 2 to 

45 lamps of 1200 candle- 
power. 

Although now su- 
perseded by the larger 
multipolar machines, so 
many bipolar machines 
are still in use that I 
consider it advisable to 
publish the following in- 




JOG HANDBOOK ON ENGINEERING. 

structions for operating and making such repairs as become nec- 
essary after the long service which thousands of these machines 
have undergone. 

The general construction of the bipolar machine is shown on 
page 105. Four field spools are provided, one pair to each side 
of the armature. The field cores are bolted to vertical yokes at 
each end of the machine, which also carry the bearings for the 
armature shaft. 

The machines should be set up in the manner described under 
Multipolar Generators. To operate satisfactorily, the machines 
must be kept perfectly clean, the oil cups well filled and the com- 
mutator surfaces smooth. 

The armature with its shaft may be readily removed after 
unscrewing the bolts and lifting the caps from the bearings at 
each end. 

Each coil or bobbin on the armature is wound independently, 
and may be rewound without disturbing any other part of the 
armature. The inside ends of eoils diametrically opposite are 
connected together, while their opposite ends are connected by 
means of wires running through the hollow shaft to opposite 
segments of the commutator.* 

Proper connections are made by having separate brushes for 
each commutator ring consisting of two pairs of segments. Thus 
in an eight coil machine, the lower brush on one commutator ring 
is connected to the upper brush on the next ring. 

The commutator segments are mounted on an insulated body, 
and when worn out may be easily replaced. 



* That is for 2000 and 1200 candle-power machines. On machines for 
4000 candle-power, each pair of opposite coils is connected in multiple 
instead of as above described. 



HANDBOOK ON ENGINEERING. 



107 



CONNECTIONS OF NO yh AND NO. 8 BIPOLAR GENERATORS. 

The field switch on the No. 7J and No. 8 machines is dif- 
ferent from that of the smaller sizes, and there is but one small 
binding post for connection to the regulator. The internal con- 
nections of the regulator are also slightly different. The inside 







Fig. 4. 

terminal of one upper binding post K (see Fig. 4), is connected 
to the positive (left-hand) wire which connects the main binding 
post to the magnets M. 

As the No* 7 J and No. 8 machines have three commutator 
rings, cross-connections between the brushes are required as 
shown in the diagram. The outside left-hand brush is connected 
across to the middle right-hand brush, and the middle left-hand 
brush is connected to the inside right-hand brush. The inside 
left-hand brush is connected to the fields, and to the shunt 
leading to the regulator. On the old type machines, the inside 
left-hand brush is connected to the right-hand small binding 
post. 



108 



HANDBOOK ON ENGINEERING. 



AUTOMATIC REGULATOR FOR BIPOLAR BRUSH ARC GENE- 
RATORS. 



The Brush Automatic Regulator or " Dial " is shown in the 
accompanying illustration. It contains a variable resistance which 

is connected as a shunt to the 
fields, and automatically changed 
to increase or decrease the field 
current, and thus the voltage of 
the machine. The resistance is 
composed of columns of carbon 
plates which rest on the lever L. 

When the current rises above 
normal, the magnets M draw up 
the lever Li and congress the car- 
bon columns, reducing their resist- 
ance and shunting more current 
from the fields. The electromo- 
tive force of the generator is thus 
reduced and the current maintained 
constant. As the resistance of the 
line is increased by the addition of 
lamps, the current in the magnets 
M is diminished and the lever 
drops, separating the carbons and increasing the resistance of the 
shunt. More of the current must then pass through the genera- 
tor fields and raise the electromotive force of the machine. 

The dash pot P is to prevent sudden changes of resistance, 
and should be kept full of pure cylinder oil or glycerine. It 
should move easily, so that the regulator can respond quickly to 
changes in the current. 




HANDBOOK ON ENGINEERING. 109 

The variable resistance W, which is adjusted by the spring S, 
is connected as a shunt to the magnet coils M and regulates their 
current. The opening of the contact G is adjusted by the fiber 
nut N. With the shunt resistance properly adjusted and the 
lever in a midway position, the current can be increased by 
tightening the nut N> and decreased by loosening it. When 
the shunt resistance W is once properly adjusted, it should not 
be changed, unless the magnets M are changed. 

To connect the regulator into the circuit, the main line is 
brought in at the large binding posts B, the positive being con- 
nected to the left-hand binding post. The current must enter at 
the left hand. 

The small Binding post J is connected with the small binding 
post on the generator, so that the carbon resistance plates are in 
shunt with the field of the generator. 

While adjusting the regulator, the generator should run at 
normal speed, and the first test should be made on short circuit. 
If the current is too low, lever L should begin to drop at 
once and so increase the current. If this lever should stand at 
its lowest position and the current still remain too low at full 
load, the speed of the generator must be increased. If the current 
is too high, the lever should rise and so reduce it ; if it fails to 
rise, the contact G should be examined. The current at this 
contact should spark all the time. If the lever rises when the 
contact is below normal the nut JSf should be tightened. 

The resistance of the shunt W should be so adjusted by 
removing the spring S that the lever will rise when the contact is 
opened and descend when the contact is closed. 

Once in six months the carbon resistance columns should be 
loosened up and the dust and loose carbon particles blown out 
with a bellows. The regulator must then be readjusted. 



110 HANDBOOK ON ENGINEERING. 



MULTIPOLAR BRUSH ARC GENERATORS. 

Each machine is provided with an iron bed-plate fitted with 
a ratchet and screw for sliding the machine to adjust the belt 
tension. This bed-plate should be securely fastened to a dry 
wood sub-base not less than 10" in thickness, except on wood 
floors, in which case it may be somewhat less, according to the 
thickness of the floor. 




Multipolar Brush Arc Generator. 

Unless the generator can be set up on a substantial floor a 
foundation of masonry must be built. 

In whatever manner the bed-plate is mounted, the greatest 
care must be taken to have a thorough and permanent insulation 
from earth. 



HANDBOOK ON ENGINEERING. 



Ill 



Four short bolts pass through the generator frame and are 
used to hold the machine in position on its bed-plate. They are 
inserted in the slots in the iron base-plate and provided with 
square nuts at their lower ends. 

The lower half of the frame is first placed in position on the 
bed -plate and bolted down, 




Method of Suspending Armature. 

The lower halves of the bearing boxes should be removed 
and the oil chambers thoroughly cleaned and filled with a good 
quality of stringy oil, to the height indicated by the mark on the 
oil gauge. The lower halves of the bearing boxes may then be 
replaced. 

The proper method of suspending the armature is shown on 
page 111. 

When handling the magnet yokes, a rope sling should be 



112 HANDBOOK ON ENGINEERING. 

used, as shown in the illustration above. The bolts should be 
inserted as shown, and as the yoke is lowered, these will act as a 
guide and drop it into its proper place. The frame bolts must be 




Method of Handling the Magnet Yoke. 

screwed up especially tight, as any movement of the yokes while 
the machinery is running will ruin the armature. 

The brush-holder yoke and the regulator rocker arm should 
be put in place with a little oil on the bearing seats to insure free- 
dom of movement through the entire range. 

SETTING THE BRUSHES. 

A pressure brush should always be used over the under brush, 
as it improves the running of the commutator and secures a bet- 



HANDBOOK ON ENGINEERING. 



113 



ter contact on the segment. The brushes should be set 5-i" from 
the front side of the brass brush-holder. 

In setting the brushes, commence with the inner pair and set 
one brush about 5|" from the holder to the tip of brush, then 
rotate the rocker or armature until the tip of the brush is exactly 
in line with the end of a copper segment, as shown in Fig. 5. 
The other brush should be set on the corresponding segment 90 o 
removed , but if the length of the brush from the holder is less than 
5 1", move both brushes forward until the length of the shorter 
brush from the holder is 5J". Now set the two extreme outer 
brushes in the same manner, 
clamping firmly in position, 
and by using a straight edge 
or steel rule, all the brushes 
can be set in exactly the 
same line and firmly se- 
cured. The spark .on one 
of the six brushes may 
be a trifle longer than on 
the others. In this case, Fig. 5. 

move the brush forward a 

trifle so as to make the sparks on the six 
brushes about the same length. Equality in 
the spark lengths is not essential, but it gives 
at a glance an indication of the running condi- 
tion of the machine. 

Brushes should not bear on the commutator 
as illustrated in Fig. 6 ; they will tend to drop 
into the commutator slots and pound the copper 
tip of the wood block. If the bearing is too far 
from the end, as in Fig. 7, the point of the brush 
is lifted from the leaving end of the segment, 
causing sparking. 

8 





Fig. 7. 



114 HANDBOOK ON ENGINEERING. 

Fig** 8 shows correct setting. 

CARE OF COMHUTATOR. 

Fig. 8. If the commutator needs lubrication, oil it 

very sparingly. Once or twice during a run is 

ample. If the oil has a tendency to blacken the commutator 

instead of making it bright, wipe the commutator with a dry 

cloth. 

The machine, of course, generates high potential, and the 
cloth, or whatever is used to oil the commutator, should, there- 
fore, be placed on a stick so that the hand is not placed in any 
way between the brushes. 

A rubber mat should be provided for the attendant to stand 
on when working around the commutator and brushes. 

To prevent any possibility of shock, all switches on the termi- 
nal board should be closed. 

As soon as the current is shut off from the machine, the com- 
mutator should be cleaned. A piece of very fine sandpaper held 
against the commutator under a strip of wood for about a minute 
before the machine is stopped, will scour the commutator suffi- 
ciently. The brushes need not be removed. Never use a file, 
emery cloth, or crocus, on the commutator. New blocks will some- 
times cause flashing, due to the presence of sap in the wood. 

CONNECTIONS OF HULTIPOLAR BRUSH ARC GENERATORS. 

Connections of Multipolar Brush Arc Generators are shown 
in Diagram No. 13442. The current enters the field from the 
negative side of the circuit and takes the following course: Spool 
1, to 2, to 7, to 8, to 5, to 6, to 3, to 4, to terminal board, to 
commutator. The field current is in the same direction for clock- 
wise and counter clockwise machines. 



HANDBOOK ON ENGINEERING, 



115 







NIC; 
•■-.. . 2 




2 r 






r ...?.- .&.. 






1 


















1 Z„ ,'-'. 


f 'l :;; >■ 






1 °- 






CsN 









E. £3 







Diagram No. 13442. 



116 



HANDBOOK ON ENGINEEKING. 



The current of the Brush Arc Machine is automatically main- 
tained constant by a regulator of one of the forms described on 
the following pages. 

FORM i REGULATOR FOR MULTIPOLAR BRUSH ARC GENE= 
RATORS. 

The Form i Regulator is placed on the frame of the machine 




To Controller 



Fig. 9. 



^Xs To Control !er 



beneath the commutator, and a constant motion is imparted to its 
main shaft through a small belt running around the armature 



HANDBOOK ON ENGINEERING. 117 

shaft. (See Fig. 9.) By means of magnetic clutches and 
bevel gears, a pinion shaft is rotated, which moves the rack and 
the rocker arm and so shifts the brushes on the commutator ; at 
the same time the rheostat arm is moved over the contacts to cut 
resistances in or out of the shunt around the field circuit. 

The ' cut tent for the magnetic clutches is regulated by the 
controller. 

The controller consists principally of two magnets which are 
energized by the main current and act when the current is too 
high or too low, by sending a small current to one of the clutches. 

If the controller is out of adjustment and fails to keep the cur- 
rent normal, do not try to adjust the tensions of both armatures 
at the same time. The left-hand spool I (see Diagram No. 
13454) may not take hold quickly enough, or the spool F may 
take hold too quickly. To make the adjustment, screw up the 
adjusting button K on the right-hand spool, increasing the ten- 
sion. This will have a tendency to let the current fall much lower 
before the armature comes in contact with H, to cause the cur- 
rent to increase. By simply tapping the armature G quickly with 
a pencil or piece of wood, forcing it down with its contact, and 
at the same time watching the ammeter, the current may be 
brought up to 6.8 amperes if 6.6 amperes is normal, or 9.8 if 9.6 
is normal. With the current at 6.8 amperes, which is .2 amperes 
high, the adjusting button L should be turned to increase the ten- 
sion on this spring until the armature M comes in contact with 
contact JV, which will force current down through 0. The clutch 
which pulls the brushes forward and rocks the rheostat back for 
less current will thus be energized. Repeat this adjustment two 
or three times, but do not touch the adjusting button K; adjust 
L until it is just right. 

At the side of the armature M a little wedge is screwed in by 
means of an adjusting button, and increases or decreases the 
leverage on this armature. See that this wedge is fairly well in 



118 



HANDBOOK ON ENGINEERING. 




Diagram No. 13454. 



HANDBOOK ON ENGINEERING. 119 

between the core or frame of the spool and the spring of the 
armature. The armature M may have to be taken out and the 
spring slightly bent. It is advisable to have the screw which 
passes through the adjuster button L about half way in, to allow 
an equal distance up and down for adjusting this lighter spring 
after the wedge-shaped piece is in the right position to give the 
necessary tension on the spring which is fastened to the arma- 
ture M. 

Having 1 adjusted the spool J so that the current will not rise 
above 6.8 (or 9.8) amperes, move the armature M up to contact 
^with a pencil or piece of wood, causing the current to be re- 
duced to about 6.2 (or 9.2). After the current settles at this 
point, decrease the tension on the spring which is fastened to 
armature G, allowing this armature to fall down to contact H. 
Current will then flow through Q, which will rock the brushes 
back and also move the rheostat arm for more current. As the 
spool J has been adjusted for 6.8 (or 9.8) amperes, the current 
cannot rise above that amount, no matter how the spool F is 
adjusted. 

The Two small shunt coils, R, and $, are connected around the 
two contacts singly to decrease the spark between the silver and 
platinum contacts. If they should become short circuited in any 
way, so that their resistance becomes diminished, sufficient cur- 
rent ma} 7- pass through either of them to operate the regulator. 
If unable to locate the trouble, disconnect these coils at points T 
and IT, when a thorough examination can be readily made. M 
and G need not move more than just enough to open the con- 
tact — ^y is ample. 



120 HANDBOOK ON ENGINEERING. 



STARTING THE MULTIPOLAR BRUSH ARC GENERATOR WITH 
FORM i REGULATOR. 

In starting, the lower switch, which short circuits the field, 
should be opened last. 

The switch in the left-hand corner of the controller (Diagram 
No. 13454) cuts out the two resistance wires which are used to 
force the current through wires O and Q to the clutches. Open 
this switch. Unclasp the brush rocker from the rheostat rocker. 
Move the brushes by hand to give the proper spark, allowing the 
rheostat arm to be moved by the controller. After the switches 
are opened, the rhoestat arm will go clear around to a full load 
position, and then, the controller takes hold and brings the arm 
back. In the meantime, rock the brushes forward or backward 
and keep the spark about the proper length, say i" at full load to 
|" on short circuit. Gradually the rheostat arm will settle, the 
spark will become constant, and the machine will give its proper 
current. Then clamp the rocker and rheostat arm together and 
let the machine regulate itself. 



FORM 2 REGULATOR FOR MULTIPOLAR BRUSH ARC 
GENERATORS. 

The connections of the Form 2 Kegulator are shown in Fig. 
10. The regulator performs two operations ; sweeps a set of 
contacts, throwing more or less resistance in shunt with the 
field circuit, and at the same time, rocks the brushes so that the 
spark is kept at proper length, varying at from J" at full load to 
|" on short circuit. 

A small belt runs over the armature shaft M and drives the 



HANDBOOK ON ENGINEERING. 



121 



rotary oil pump P. The pump draws the oil from the containing 
case and forces it through passages to the valve T. 

The ports overlap this valve so that the oil may flow through 
when the valve is in its central position. The valve is controlled 
by the electromagnet F (Fig. 10) which actuates the armature U 




Form 2 Regulator. 



and the lever H. The pull on armature £7" varies with the strength 
of the current which excites F. The opposite end of the lever H 
is attached to spring G, which is adjusted by the screw nut R so 
as to hold the valve in central position when normal current is 
flowing through the controlling magnet. 



122 



HANDBOOK ON ENGINEERING 




Fig. 10. 



HANDBOOK ON ENGINEERING. 123 

If the current is too strong, it pulls down the armature U, 
raising the valve, throwing more oil on the upper side of the 
circular piston head S, and allowing the oil to run out from the 
lower side, thus forcing the piston X around clockwise, lowering 
the current by moving the contact arm so as to shunt more cur- 
rent from the fields, at the same time moving the brushes forward 
until the current returns to its normal value. 

If the current is too low the operation is reversed. 



ADJUSTMENT OF FORH 2 REGULATOR. 

To raise the current, turn the hard rubber nut R (Fig. 10) to 
the right. If the current is too high, turn the nut to the left. 

The limits between which the regulator operates are deter- 
mined by the number of turns in the spring G. If the spring G 
is stiffened by cutting off some of the turns and stretching it out, 
the limits of regulation will be wider. If the spring has a greater 
number of turns, it will regulate within narrower limits, but be 
more liable to " pump." 

The regulator may be caused to operate quickly in one direc- 
tion and slowly in the reverse direction by changing the position 
of the stops on lever H. By raising the stop on the right-hand 
side of lever H, the movement on increasing the current will be 
retarded. 



STARTING THE MULTIPOLAR BRUSH ARC GENERATOR WITH 
FORM 2 REGULATOR. 

Before starting the machine, the oil box of the regulator should 
be filled with a light spindle or dynamo oil nearly up to the shaft 
which carries the contact arm, etc. 

If the pump fails to start promptly, it may be started by shift- 



124 HANDBOOK ON ENGINEERING. 

ing the brushes backward and forward, and moving the contact 
arm. 

In a newly installed machine, the oil should be changed at 
least once a week. 

Having correctly adjusted the regulator for the desired cur- 
rent, as previously described, the starting valve handle S 1 (Fig. 
10) should be turned counter clockwise when the machine is 
running without load. This handle operates a valve which con- 
nects both sides of the circular cylinder, thereby giving a free 
flow of oil between the two sides, and preventing the operation of 
the piston and relieving the pump from any undue loado 

To put the machine in operation, the valve should be gradu- 
ally thrown around clockwise, cutting off the flow of oil from the 
two sides of the cylinder after the switches have been opened. 
This valve may also be used to throw the regulator out of opera- 
tion if desired. 

FORM 3 REGULATOR FOR MULTIPOLAR BRUSH ARC GENE- 
RATORS. 

In the Form 3 Regulator a belt from the armature shaft runs 
a small countershaft with crank attached. A rocking or recipro- 
cating motion is thus imparted to the main lever, on which are 
pivoted two self-adjusting clutch jaws or grips. When the cur- 
rent is normal, the clutches are held stationary, but as the current 
varies, either above or below normal, the clutch on one side is 
dropped so that it will grip the clutch disk, and the mechanism 
revolves in the proper direction to restore the current. 

With slight variations of the current, the regulator contact 
arm is moved forward or backward very slowly ; while, with 
greater variations, caused by any considerable number of lamps 
being cut in or out, the movement is increased and the normal 
point or position more quickly reached. 



HANDBOOK ON ENGINEERING. 125 

For starting- Brush Arc Generators with Form 3 Regulators, 
see general directions under Form 1 Regulator. 



FORM 4 REGULATOR FOR MULTIPOLAR BRUSH ARC GENE- 
RATORS. 

The Form 4 Regulator is similar to the Form 3 ; the counter- 
shaft and rocking lever are identical, but instead of using clutches, 
the lever operates two pawls, which engage in ratchet wheels. 
The pawls are not in contact when the current is normal, but are 
thrown in to move the arm to either right or left as the current 
varies and the regulator is called upon to shunt more or less cur- 
rent from the held. 

AMMETER. 

A reliable ammeter should always be connected in the circuit 
of an arc generator, so that the exact current may be read at a 
glance. It should be connected into the negative side of the line 
where the circuit leaves the regulator. 



INSTRUCTIONS FOR INSTALLING AND OPERATING IHPROVED 
BRUSH ARC LAMPS. 

Suspension. — One of three methods of suspension may be 
used for Brush Arc Lamps. If chimney suspension, which is the 
most common, is adopted, the wire, cable or rope used to suspend 
the lamp must be carefully insulated from the chimney. For this 
purpose a porcelain insulator should be inserted between the 
support and the lamp. 

Hook suspensions may be used to advantage in some places, 
but greater care must be taken to insulate the supporting wires 
from any conductors, as the hooks form the terminals of the lamp. 



126 HANDBOOK ON ENGINEERING. 

The most convenient arrangement for indoor use is to suspend 
the lamp from a hanger board. The porcelain base of the hanger 
board prevents short circuits or grounds. 

The lamps run nominally on circuits of (3.6 amperes for 1200 
candle-power and 9.6 amperes for 2000 candle-power. In case 
it is necessary to run a lamp on a circuit differing from the 
standard, the lamp may be adjusted by moving the contact on 
the adjuster. This will compensate for about one ampere either 
way from normal and is set in about the middle position when 
the lamp is shipped. 

Permanent adjustment for special circuits of variation greater 
than one ampere from standard is made by filing the soft iron 
armature. The clutch should be so adjusted that the center of 
the armature is ±f above the plate when the trip on the first rod 
is touching the bushing and J J'' when the trip on the second rod 
is in a similar position. A small gauge is convenient for adjust- 
ing the clutch. The position of the trip of the clutch determines 
the feeding point of the lamp. 

After thoroughly repairing and cleaning the lamp, it should be 
run a short time before installing. Lamps should not be tested in 
an exposed place, as a strong draft of air will cause unpleasant 
hissing, which may be mistaken for some internal trouble. 

Lamps should not hiss or flame if good carbons are used. A 
voltmeter should always be used when adjusting or testing. 

Connecting* — The lamp terminal hooks are marked P (posi- 
tive) and N (negative), and should be connected into circuit 
accordingly. 

The carbons should rest in contact when the lamp is cut out. 
When the switch is opened, part of the current from the positive 
terminal hook (P) goes through the adjuster to the yoke, and 
thence through the carbon rod and carbons to the negative ter- 
minal hook (N). The remainder of the current goes to the cut- 
out block, but, as the cut-out is closed at first, the current crosses 



HANDBOOK ON ENGINEERING. 127 

over through the cut-out bar to the starting resistance, and so to 
the negative side of the lamp. A part of it, however, is shunted 
at the cut-out block through the coarse wire of the magnets, and 
so to the upper carbon rod and carbons and out. This shunted 
current energizes the magnets and so raises the armature which 
opens the cut-out and at the same time establishes the arc by 
separating the carbons. 

Trie fine wire winding" is connected in the opposite direction 
from the coarse winding, and its attraction is therefore opposite. 
When the arc increases in length, its resistance increases, and 
consequently, the current in the fine wire is increased. The 
attraction of the coarse wire winding is, therefore, partly overcome 
and the armature begins to fall. As it falls, the arc is shortened 
and the current in the fine wire decreases. The mechanism feeds 
the carbons and regulates the arc so gradually that a perfectly 
steady arc is maintained. 

The fine wire of the magnets is connected in series with the 
winding of a small auxiliary cut-out magnet at the top of the 
mechanism. 

This magnet, which also has a supplementary coarse winding, 
does not raise its armature unless the voltage at the arc increases 
to 70 volts. The two windings connect at the inside terminal 
on the lower side of the auxiliary cut-out magnet, and the current 
from the fine wire of the main magnets passes through both wind- 
ings and then to the cut-out block and so to the starting resist- 
ance and out. 

If the main current through the carbon is interrupted (as by 
breaking of the carbons), the whole current of the lamp passes 
through the fine wire circuit. Before this excessive current has 
time to overheat the fine wire circuit, it energizes the auxiliary 
cut-out magnet and closes a circuit directly across the lamp 
through the coarse wire on the auxiliary cut-out to the main cut- 
out block, and thence to the negative terminal. 

The auxiliary cut-out operates instantly and prevents any dan- 



128 



HANDBOOK ON ENGINEERINGS 



ger to the magnets during the short period required for the main 
armature to drop and throw in the main cut-out. When the main 




CONNECTIONS FOR IMPROVED BRUSH ARC, LAMPS. 

cut-out operates, the armature of the auxiliary cut-out fails, because 
there is not sufficient current in that circuit to energize the magnet. 



HANDBOOK ON ENGINEERING. 129 

The voltage at which the auxiliary cut-out magnet operates 
depends on the position of its armature, which is regulated by 
the screw securing the armature in position. It should not be 
adjusted to operate at less than 70 volts. 

The carbons should be solid and of uniform quality. For the 
best results, the upper carbon should be 12"x T 7 g-", and the 
lower 7" x T 7 ^ " . The stub of the upper carbon may then be used 
in the lower holder when retri mining. 

At each trimming the rod should be carefully wiped with 
clean cotton waste. It should never be pushed up into the lamp 
in a dirty condition. 

In order to remove the carbon rod or examine the mechanism, the 
jacket must be lowered by pressing a spring clip on its under side. 

The carbon rod may be unscrewed and removed by a small 
screw-driver or small strip of jnetal inserted in the slot cut in the 
rod cap. The cap will remain in the hole through the yoke when 
the rod is taken out. 

The lamp must never be left burning with the jacket off, nor 
be allowed to hang with the mechanism exposed to the weather. 

PERSONAL SAFETY. 

Never allow the body to form part of a circuit. While ftand- 
ling a conductor, a second contact may be made accidentally 
through the feet, hands, knees or other part of the body in some 
peculiar and unexpected manner. For example, men have been 
killed because they touched a ;t live" wire while standing or 
sitting upon a conducting body. 

Rubber gloves or rubber shoes, or both, should be used in 
handling circuits of over 500 volts. The safest plan is not to 
touch any conductor while the current is on, and it should be 
remembered that the current may be present when not expected, 
due to an accidental contact with some other wire or to a change 



130 



HANDBOOK ON ENGINEERING. 



of connections. Tools with insulated handles, or a dry stick of 
wood, should be used instead of the bare hand. 

The rule to use only one hand when handling dangerous elec- 
trical conductors or apparatus is a very good one, because it 
avoids the chance, which is very great, of making contacts with 
both hands and getting the full current right through the body. 
This rule is often made still more definite by saying, " Keep one 
hand in your pocket," in order to make sure not to use it. The 
above precautions are often totally disregarded, particularly by 
those who have become careless by familiarity with dangerous 
currents. The result of this has been that almost all the persons 
accidentally killed by electricit}^ have been experienced electric 
linemen or stationmen. 



TABLE SHOWING RELATIVE RESISTANCE OF METALS AT TEMPERA- 
TURE OF 70 DEGREES F. 



NAME OF METAL. 


Resistance in Ohms of Wire 100 ft. long and 
one-thousandths of an inch in diameter. 




965 

1,030 

1,328 

1,900 

3,600 

5,700 

6,400 

7,500 

8,500 

12,600 

12,700 

23,000 

42,000 

57,700 

3,792,000 


Remarks. 


Silver 




Copper 


The resistance of arc light car- 


Gold 


bons is given for comparison and, 


Aluminum 


as will be noticed, it is about 


Zinc 


4000 times as great as that of 


Platinum 


silver. 


Iron, Wrought .. 

Nickel 


To obtain the resistance of 


Tin 


100 ft. of wire of any size, divide 


German Silver 

Lead 


the figures in this table by the 
square of the diameter of the 




wire in thousandths of an inch. 


Manganese Steel.... 
Mercury 




Arc Light Carbon .. 





HANDBOOK ON ENGINEERING. 



131 




Fig. 1. The Thomson-Houston Standard Arc Dynamo 
Arranged for Right-hand Rotation. 



CHAPTER X. 

INSTALLATION OF ARC DYNAMOS. 

Location and mounting, — The generator should be located 
in a cool, dry room, free from dust, metal chips or flying parti- 
cles of any sort. Space should be allowed around the machine 
to give ample room for reaching all parts of it, particularly the 
commutator. The generator should be set upon a firm founda- 



132 HANDBOOK ON ENGINEERING. 

tion of well-seasoned wood, and should be mounted upon a 
sliding bed-plate, so that the belt can be tightened or loosened 
while the generator is running. The generator should be 
thoroughly insulated from earth. The sliding bed-plates as now 
manufactured are designed to provide perfect insulation, and 
meet this requirement fully. The direction of rotation of the 
armature in the standard generator is from right to left, or 
counter-clockwise, as seen when facing the commutator. This is 
called a right-hand machine. Right-hand machines may be run 
left-handed by replacing certain parts of the brush-holder and 
regulating mechanism. 

Pulleys* — The generator is provided with a pulley of proper 
size to transmit the power demanded. 

Bearings* — The oil in the reservoir should be renewed once a 
week for the first two or three weeks. 

Speed. — The generator should be run as nearly as possible at 
the speed given by the maker. An increase of speed, if not too 
excessive, will do no harm, but a considerable diminution in 
speed below normal, when the generator is doing its maximum 
work, is liable to cause unsteadiness in the lights. 

The automatic regulator will adjust perfectly for fluctuations 
in speed near or above normal, unless the fluctuations are 
extremely sudden, as in the case of slipping of the belt. 

Belts* — The belt should be about half an inch narrower than 
the face of the pulley. An endless belt is desirable. 

Brushes* — When the generator is in position the brushes or 
strips of copper B B, B l B l (see Fig. 3), are placed on the 
machine in the manner shown. All four brushes should be set 
exactly to the gauges sent with each machine, so that they press 
with sufficient force on the surface of the commutator to insure 
good contact at all times. 

The length of the gauge is such that the brushes project a 
little past the center of the commutator, as shown in Fig. 5, to 



HANDBOOK ON ENGINEERING. 



133 




=Q= 




CONNECTIONS FOR ARC LIGHTING SYSTEM. 

Fig. 2. 



134 



HANDBOOK ON ENGINEERING. 



avoid catching in the slots should the armature be turned back- 
ward. 

Air Blast* — - The air blast or blower plays an important part 
in the successful operation of the machine. The air blast requires 
no attention, except that it should be kept scrupulously clean and 
well oiled. Only the best quality of mineral oil should be used. 
Poor oil will always cause trouble. 

The screens which cover the air inlets on the air blast, should 




CONNECTIONS FOR RHEOSTAT. 

Fiff. 3. 



be kept clean and free from dust. They should be taken out 
about once a month and cleaned in kerosene oil. 

Regulator* — The regulator is fastened to the frame of the 
machine by two short bolts, as shown in Fig. 2. On the left- 
hand machine, i. e., one which runs clockwise, its position is on 
the opposite side. Before filling the dash-pot D with glycerine, 
see that the regulator lever and its connections, brush yokes, etc., 
are free in every joint, and that the lever L can move freely up 
and down. Then fill the dash-pot D with concentrated glycerine, 



HANDBOOK ON ENGINEERING. 



135 



The long wire from the regulator magnet M, is connected with 
the left-hand binding post P of the machine, and the short wire 
with the post P 2 on the side of the machine. The inside wire 
of the field magnet, or that leaving the iron flange of the left-hand 
field should be connected into the post P 2 also, as shown in Fig. 
2. The electric circuit (see Fig. 3), should be complete from 




CONTROLLER FOR ARC DYNAMO. 

Fig. 4. 

P 1 on the controller magnet, through the lamps to post JV on the 
machine, through the right-hand field magnet C 1 , to the brushes 
B 1 B 1 , through the commutator and armature to the brushes 



136 HANDBOOK ON ENGINEERING. 

B B, through the left-hand field 0, to posts P 2 and P, thence to 
posts P 2 and P on the controller magnet, through the controller 
magnet to P 1 . The current passes in the direction indicated by 
the arrows. 

Controller* — The controller magnet (see Fig. 4) is to be fast- 
ened securely by screws to the wall or some rigid upright support, 
taking care to have it perfectly plumb. It is connected to the 
machine in the manner shown in Fig. 3, i. e., the binding post 
P 2 on the controller magnet, is connected to the binding post P 2 
(see Fig. 2) on the end of the machine ; and likewise, the post 
P on the controller to the post P on the leg of the machine ; the 
post P 1 forms the positive terminal from which the circuit is to 
run to the lamps and back to AT. 

Great care should be take . to see that wires P P and P 2 P 2 
are fastened securely in place ; for if the connection between P 
and P should be impaired or broken, the regular magnet M would 
be thrown out of action, thus throwing on the full power of the 
machine, and if the wires P 2 P 2 should become loosened, the full 
power of the magnet M would be thrown on, and the regulator 
lever L, rising in consequence, would greatly weaken or put out 
the lights. 

The wires leading from the controller magnet to the machine 
should have an extra heavy insulation. Care should be taken in 
putting up the controller magnet that the following directions are 
followed : — « 

(1) The cores B of the axial magnets G C must hang exactly 
in the center, and be free to move up and down. 

(2) The screws fastening the yoke or tie pieces to the two 
cores must not become loosened. 

. (3) The contacts O must be firmly closed when the cores are 
not attracted by the coils C C, which is the case, of course, when 
no current is being generated by the machine, and when the cores 



HANDBOOK ON ENGINEERING. 137 

are lifted, the contacts must open from ^" to g 1 ^" ; a greater 
opening than ^" has the effect of lengthening the time of action 
of the regulator magnet. This tends to render the current un- 
steady, and in case of a very weak dashpot or short circuit, might 
cause flashing. If this adjustment is not properly made there 
will be destructive sparking on a small portion of the contact sur- 
faces. 

(4) All connections must be perfectly secure. 

(5) The check-nuts A 7 " must be tight. 

(6) The carbons in the tubes L must be whole. 

These carbons form a permanent shunt of high resistance, 
around the regulator magnet M, and if broken will cause destruc- 
tive sparking at contacts 0, burning them and seriously interfer- 
ing with close regulation of the generator. In case a carbon 
should become broken, temporary repairs may be made by splic- 
ing the broken piece with fine copper wire. To keep the action 
of the controller perfect, the contacts should be occasionally 
cleaned by inserting a folded piece of fine emery cloth and draw- 
ing it back and forth. 

The amount of current generated by each machine depends 
upon the adjustment of the spring S. If the tension of _ this 
spring is increased, the current will be diminished ; if the tension 
is diminished, the current will be increased. 

Once set up and in perfect working condition, adjusted to the 
proper current, the controller magnet should rarely need any 
adjustment. 

Testing arc light dynamos. — The commutator should fit the 
shaft snugly, but be sufficiently free to turn easily on the shaft. 
Be very careful to put the short brush-holders on the outer yoke, 
and the long brush-holders on the inner yoke. Also see that the 
long binding post, attached to the sliding connection, is on the 
lower left-hand brush-holder, and the short post on the lower right- 



138 



HANDBOOK ON ENGINEERIEG. 




G 




A — Commutator Segments. 
g 4 | Primary Brushes. 



» 8 J Secondary Brushes. 



C— Forward Point of Segment. 
D— Point of Brush. 
E — Brush-holders. 
F — Point of Contact. 



Figs. 5 and 6. 



HANDBOOK ON ENGINEERING. 139 

hand brush-holder. Always set the brush-holders to the proper 
angle by the brush-holder gauge. First tighten up the brush-hold- 
• ers and then turn them to the correct position by means of a piece 
of steel wire passed through the holes. Then permanently tighten 
up the brush-holders very firmly, trying them with the gauge to 
see that they are the same distance from the commutator. Always 
be careful to get the brushes exactly straight and flat before 
clamping them to the brush-holders, and always set them to the 
exact length of the brush gauge. 

Setting the cut-out* — After the brushes are in position, the 
cut-out must be set. This is done by turning the commutator on 
the shaft in the direction of rotation (if the commutator is set in 
position the whole armature must be revolved), until any two seg- 
ments are just touching the primary brush on that side, as seg- 
ments A' and A" ' touch brush B 1 in Fig. 6. Under these 
conditions brush B 4 should be at the left-hand edge of upper 
segment. Then turn commutator until the same two segments are 
just touching brush jB 2 , when the end of brush B 3 should just 
come to the right-hand edge of the lower segment. If the second- 
ary brush projects beyond the edge of the segment the regulator 
arm should be bent down ; if it does not come to the edge of the 
segment the arm should be bent up. 

Care must be taken that the regulator armature is down on the 
stop when the cut-out is being set. 

Always try the cut-out on both primary brushes. If it does 
not come the same on both, turn one over. If the brush-holders 
are correctly set by the gauge, there should be no trouble in get- 
ting the cut-out set properly after one or two trials. 

The distance from the tip of the brush, which is on top, to the 
left-hand edge "of No. 2 segment on a right-hand machine, or to 
the right-hand edge of No. 3 segment in a left-hand machine, is 
called the lead, and should be made to correspond to the follow- 
ing table : — 



140 HANDBOOK ON ENGINEERING. 



TABLE OF LEADS. 



DRUM ARMATURES. 


RING ARMATURES. 


C 12 J" positive. 


K 12 T 3 ^-" positive. 


C2 3" U 
^ 8 • 


K 2 i" " 

iV 8 


E12yV u 


M 12 J" negative. 


E 2 } " u 


M 2 i" " 


H^i" " 


LD 12 J" positive. 


H 2 1" U • 


LD2," J, 




MD 12 -i§" '.' 




MDHf" " 



Place the screws in the binding posts at the lower ends of the 
sliding connections and put on the dash-pot connections between 
the brushes, with the heads of the connecting screws outward. 
In every case the barrel part of the dash-pot is connected to the 
top brush-holder, and plunger part to the bottom brush-holder. 
See that the field and regulator wires are connected and that all 
connections are securely made. When all connections have been 
made, make a careful examination of screws, joints, and all mov- 
ing parts. They must be free from stickiness, and not bind in 
any position. 

To determine when -the machine is under full load, notice the 
position of the regular armature, which should be within i" of 
the stop. At full load the normal length of the spark on the com- 
mutator should be about T 3 F " . If it is less than this, shut down 
the machine and move the commutator forward, or in direction of 
rotation until the spark is of the desired length. If the spark is 
too long, move the commutator back the proper amount. 



HANDBOOK ON ENGINEERING. 



141 



BEST POSITION OF AIR BLASTS AND JETS ON 
LD AND MD DYNAMOS. 




Lift Regulator as high as oossiWe, 
Figs. 7 and 8. 



142 HANDBOOK ON ENGINEERING. 



DIRECTIONS FOR SETTING THE AIR BLAST JETS ON LD AND 
MD DYNAMOS. 



With new segments* — Loosen bolts A-A-A-A and turn the 
air-blast so as to bring the bolts in the centers of the slots 
B-B-B-B. Set the brushes by the gauge. Lift the regulator 
lever as high as possible and set the point D of the air blast jet 
•J^" in front of the point P of the brush A. Place the lower jet 
in the same relative position with the lower brush. 

As segments wear down, — Loosen the bolts A-A-A-A and 
follow up the wear of the segments by turning the air blast against 
direction or rotation of armature as indicated. Turn the point 
of the jet downward, so as to blow more directly through the slot 
between the segments. Set the lower jet in the same relative 
position with the lower brush. 



SOME TROUBLES WHICH MAY BE HET AND THEIR 
CAUSES — REVERSAL OF POLARITY. 

Cases are frequently reported where generators, from lightning 
discharges, wrong plugging on switch-board, or some other 
reason, suffer a reversal of polarity. The effect of reversal is 
that the lamps in circuit with the machine burn "upside down ; " 
which has the effect of throwing much of the light up instead of 
down, and with some carbons the arc will flame badly. This can 
be remedied temporarily, by changing the plugs on the switch- 
board, so that the current will enter the line where ordinarily it 
returns. 

Occasion should be taken, however, as soon thereafter as 



HANDBOOK ON ENGINEERING. 143 

possible, to properly magnetize the fields so that they will be the 
right polarity, as follows : — 

Close the armature short circuiting switch on the frame of the 
machine and run a loop from some other arc generator which 
happens to be in operation. Connect the positive side of this loop 
to the lower binding post N on the right leg of the machine, and 
the negative side of the binding post P 2 on the end of the frame 
under the regulator. Then open the armature short circuiting 
switch on the second generator. A very few seconds will suffice 
to correctly polarize the first machine. 

To detect a short circuit in the field, make all adjustments as 
if working under normal conditions, then run the machine at the 
proper speed on a dead short circuit. If there is no short circuit 
in the field, the armature of the regulator will be drawn up hard 
against the bottom of the magnet, but if there is a short circuit in 
the field the armature will drop more or less according to the 
amount of field wire cut out of circuit. 

To find out which half of the field is affected, close the field 
switch and remove the regular wire from the Post P 2 , Fig. 2, then 
connect posts P 3 and N to some source of direct current, as a 
110-volt exciter, and with a volt-meter measure the drop in 
voltage between posts N and A 1 and between A and P 2 . The 
drop should be very nearly the same in both cases if the winding 
is perfect, but the drop will be less across that field which is 
short circuited. 

Another trouble which is liable to be met in flashing. When a 
generator flashes an arc is drawn around the commutator from 
one brush to the other, which soon short circuits the armature, 
putting out the lights. This arc is usually broken very quickly, 
but the flashing may be repeated at frequent intervals. There 
are several causes of flashing, such as overload, low speed, stick- 
iness in the regulating mechanism, short circuit in the field, com- 
mutator not in proper position , or a dash-pot which is too stiff or 



144 



HANDBOOK ON ENGINEERING. 



too loose. If a machine flashes when running under proper load 
and at proper speed, see that there is no stiffness in the regulating 
mechanism, then examine the cut-out and note the length of the 
spark, which should be about T 3 g-" long at full load. 

If all these adjustments are right, make the test described 
above for a short circuit in the fields. 



RING ARMATURES. 

All K, M, LD and MD machines are now made with ring 
armatures. 

A recent improvement in the construction of these armatures 
consists in the removal of all insulation from the cores and the 
addition of more insulation to the separate coils. The cores are 
divided into three sections with ventilating spaces between* 




Armature Core and Winding. 
Fig. 9. 



By removing the insulation from the cores these new coils may be 
applied to any of the older armatures now in use. 



HANDBOOK ON ENGINEERING. 



145 



In case it becomes necessary to remove a faulty coil, the follow 
ing directions should be carefully followed : — 




Armature Spider and Shaft. 
Fig. 10. 



DIRECTIONS FOR PLACING COILS IN RING ARMATURE 
WITH INSULATED CORE. 



After the armature has been taken out of the machine, remove 
the brass binding wire by cutting the bands, carefully covering 
all the exposed parts of the armature with a cloth, so as to pre- 
vent filings from lodging on the winding. Remove the cord 
and the tape from the joints of the lead wires and cross connec- 
tions, at each end of the armature. Take out the lead wires and 
remove the wooden disks from the shaft. These disks are held 
in place by a set-screw, passing through a brass piece let into the 
disk, and resting on the shaft. Unsolder the joints on the coils 
that are to be removed. Take out the bolts holding the two 
gun-metal spiders together, and with a long steel pin or drift, 
drive out the key, which fastens the loose spider to the shaft. 
The spider next to the pulley is securely fastened to the shaft by 
a steel pin drawn tightly into a reamed hole, passing through 

10 



146 HANDBOOK ON ENGINEERING. 

both spider and shaft. By driving on the commutator end of the 
shaft with a hard- wood block and mallet, or lead hammer the 
shaft with the fixed spider may be removed, and the remaining 
loose spider can then be driven out with the hard-wood block and 
mallet. Before removing the shaft and spiders note the position 
of the wedge in the armature core, its position is always indicated 
by the letter W plainly stamped on the hub of the loose spider. 

Remove the wood spacing blocks, slip the coils around on 
the core until the imperfect coils are over the wedge, then spread 
these coils apart so as to expose the wedge and cut away the insu- 
lation on the core for a space of 3 J" on top and bottom over the 
space containing the wedge ; the wedge may then be driven 
towards the center of the core, taking care that it does not 
drop on the coils opposite and injure them. The faulty coils 
may now be removed, new ones be inserted and the wedge 
be replaced and very carefully reinsulated. This insulation is put 
on, beginning with the layer next to iron core, as follows : — 

(1) 1 layer of paper, (5) 1 layer of mica, 

(2) 1 layer of mica, (6) 1 layer of canvas, 

(3) 1 layer of sheeting, (7) 1 layer of tape, 

(4) 1 layer of tape, (8) 1 layer of paper. 

Slip the coils around to their proper places so that they will 
be in correct position with regard to the arms of the spiders. 

The loose spider may now be put in place, and afterwards the 
fixed spider and shaft, the bolts being inserted and the nuts 
tightened up. Replace the key in the loose spider, put on the 
wooden disks and carefully solder and tape £,11 the joints of lead 
wires and cross connections. Replace the spacing blocks in their 
proper positions, solder aDd tape the connections, and the arma- 
ture is ready to be bound. 



HANDBOOK ON ENGINEERING. 



147 



The binding 1 wire used is No. 11, hard brass. The arrange- 
ment of the binding wire is clearly shown in the original bands of 
the armature and should be carefully noted before they are 
removed. The same brass clips may be used again, provided due 
care is taken in bending up the ends, when the old band is taken off. 




Standard Plug Switchboard for 6 Circuits. 
Fig. 11. 



SWITCHBOARDS. 



The standard arc lighting switchboard consists of a marble 
panel, to the back of which the conductors are attached. When 
very large boards are built they are made by combining several 
panels. Switchboards of any capacity can be constructed without 



148 



HANDBOOK ON ENGINEERING. 



difficulty. The general arrangement of conductors is the same 
for all sizes. 

Each panel is drilled with counter-sunk holes arranged in 
rows, and in each hole, a brass bushing is fitted. All the bush- 
ings of the same horizontal row on the right of the center of the 
panel are electrically connected, except those of the bottom row, 
and a similar connection is made between the bushings on the 
left of the center. A heavy brass strap is supported by the back 
of the panel behind each vertical row of holes and has bushings 
in it corresponding to those in the face of the panel. These straps 
are placed several inches back of the marble, but any one of them 
can be put in electrical connection with any horizontal conductor it 
crosses by the use of suitable brass plugs inserted in the bushings. 
In a standard panel the number of horizontal rows of holes 

equals one more than the 
number of generators. The 
vertical rows are always twice 
the number of generators. 
The positive leads of the 
generators are attached to 
binding posts on the left- 
hand ends of the horizontal 
conductors. The negative 
leads are connected to the 
corresponding binding posts 
at the right-hand end of the 
board. 

The positive line wires 

are connected to the vertical 

straps on the left, and the 

negative wires to similar straps on the right of the center of the 

panel, 

If a switchboard plug be inserted in any of the holes of the 





Back of Switchboard. 
Fig. 12. 



HANDBOOK ON ENGINEERING. 



149 



board, it puts the corresponding generator lead and line wire in elec- 
trical connection, but as the positive line wires are back of the 
positive generator leads only, it is not possible to reverse the 
connection of the line and generator accidentally, though any 
other combinations of lines and generators can be made readily 
and quickly. 

The holes of the lower horizontal row have bushings connected 



Generator 




Star-ting 

Resistance 



METER FOR STATION USE. 
CONNECTIONS FOR WATT-METERS FOR SERIES ARC CIRCUITS 

Fig. 13. 



with the vertical straps only. Plugs connected in pairs by flexible 
cable and inserted in the holes put the corresponding vertical 
straps in connection as needed, and normally independent lines 
may be connected when one generator is required to supply 
several circuits. 

Lines and generator leads may be transferred, while running, 



150 



HANDBOOK ON ENGINEERING. 



by the use of these cables, without shutting down the machines 
or extinguishing lamps. 

WATT METERS. 

"Watt-meters are now built to measure the power supplied on 
series arc circuits. These watt-meters are similar in principle 




Interior of M Arc Lamp. 
Fig. 14. 

to those used on incandescent lighting systems, and, being ex- 
tremely accurate, are equally effective in preventing waste of 



HANDBOOK ON ENGINEERING. 151 

current. The watt-meters supplied to customers are made in 4 
lamp or 8 lamp capacities. An excess of voltage equivalent to 
two lamps over the rated load causes the meter to automatically 
cut out, both lamps and meters being short-circuited. This pre- 
vents the interruption of the series circuit in case of any local 
trouble with lamps or line inside the meter circuit. Station watt- 
meters are arranged to measure the total output of a generator, 
and' are made with capacities for 35, 50, 65, 80, 125 or 150 lamps. 



INSTRUCTIONS FOR THE INSTALLATION AND CARE OF ARC 
LAMP5. 



The lamps should be hung from the hanger boards provided 
with each lamp, or from suitable supports of wire or chain. 

As the hooks on the lamp form also its terminals, they should 
be insulated, where a hanger board is not used, from the chains 
or wires used to support the lamp. 

To make the upper carbon positive the wire from the positive 
terminal of the machine should be fastened into the binding post- 
hook, on the switch side of the D lamp, and on the opposite side 
in the M and K lamps. When the lamps are hung where they 
are exposed to the weather, they should be covered with a metal 
hood, to prevent injury from rain or snow. In such cases care 
should be taken that the circuit wires do not form a contact on 
the metal hood, and short-circuit the lamp. Before the lamps 
are hung up they should be carefully examined to see that the 
joints are free to move, and that all connections are perfect. 

No lamp should be allowed to remain in circuit with the 
covers removed and mechanism exposed. Such practice is 
dangerous. 



152 



HANDBOOK ON ENGINEERING. 



STARTING THE LAMPS. 

When the lamps are all in position and ready for operation 
the machine may be started, and when the armature has reached 

art- 




"w^ 



CONNECTIONS FOR M AND K ARC LAMPS. 

Fig. 15. 

its proper speed, the short-circuiting switch on the frame should 
be opened. 



HANDBOOK ON ENGINEERING. 153 

This method allows the generator to take up its load 
gradually, and is a very important point in the handling of the 
machine, particularly when series-incandescent lamps are in the 
circuit. 

The generator should be driven at its proper speed, as desig- 
nated by the maker. The regulator lever will first rise and then 
oscillate slowly up and down for short distances, as the regulator 
is cut in and out by the controller magnet. If the movements are 
too great, the lights will vary in intensity — first up, then down. 
This condition will result from a weakness of the regulator dash- 
pot. The regulator lever should always be a short distance away 
from the stop — say from J" to J" or more, according to condi- 
tions — and should always vibrate up and down in the manner 
stated. Should the lever of the regulator remain down, it shows 
that the speed of the machine is not sufficient to supply the cir- 
cuit, or that the machine is overloaded with lights. 

The controller magnet should be constantly opening and 
closing its contacts. This movement is very slight. The arc of 
the 2000 c. p. lamps should be -f^" to 1" in length and the 1200 
c. p. lamps should have an arc -J^" to y in length. If the car- 
bons are of good quality, the arc should not flame or hiss. 

INSTRUCTIONS FOR REPAIRING, TESTING AND ADJUSTING 
ARC LIGHTS. 

It frequently becomes necessary, after the lamps have been in 
use for a considerable length of time, to repair and readjust them. 

After cleaning and repairing, the lamp should be tested and 
readjusted. Experience shows that whenever even one new part 
has been put into a lamp or generator, trouble may result if tests 
and readjustments are not made before putting the apparatus into 
regular service. 

In order to properly test the lamps that have been repaired, 
select some part of the engine room where the lamps can be hung 



154 HANDBOOK ON ENGINEERING. 

up and burned without being subjected to drafts of air ; other- 
wise, they may hiss and act badly, no matter how carefully the 
adjustments may be made. 

When the lamps have been hung up and attached to the 
hanger boards, or some similar arrangement for connecting to the 
circuit in the usual manner, the carbon rods should be cleaned 
thoroughly with cotton waste. If any sticky or dirty spots 
appear, which cannot be readily removed with waste, use a piece 
of well-worn crocus cloth, always being careful to use a piece of 
clean waste before pushing the rod up into the lamp. Under no 
circumstances whatever should the rods be pushed up into the 
lamps in a dirty condition ; they should always be cleaned in the 
manner described. 

The tension of the clamp which holds the rod is adjusted by 
raising or lowering the arm at the top of the guide rod. If the 
tension is too great, the rod and clutch will wear badly and the 
feeding will be uneven, causing unsteadiness in the lights. Too 
light tension will not allow the clutch to hold up the rod and any 
sudden jar to the lamp will cause the rod to fall and the light to 
go out. 

The double carbon or M lamp should have the tension of the 
second carbon rod a trifle lighter than the first one. 

When adjusting" the tension, be sure to keep the guide rod 
perpendicular and in perfect line with the carbon rod ; it should 
be free to move up and down without sticking. 

The tension of the clutch in the D lamp should be the same as 
that of the K lamp. It is adjusted by tightening or loosening 
the small coil spring from the arm of the clutch to the bottom of 
the clamp stop. 

To adjust the feeding point in the K lamp, press down the 
main armature as far as it will go, then push up the rod about 
one-half its length, let go the armature and then press it down 
slowly, and note the distance of the bottom side of the armature 



HANDBOOK ON ENGINEERING. 155 

above the base of the carved part of the pole. When the rod 
just feeds, this distance should be J". If it is not, raise or lower 
the small stop which slides on the guide rod passing through the 
arm of the clutch, until the carbon rod will feed when the arma- 
ture is J" from rocker frame at the base of the pole. 

To adjust the feeding point of the M lamp, adjust the first rod 
as in the K lamp. Then let the first rod down till the cap at the 
top rests on the transfer lever. The second rod should feed with 
the armature at a point j 1 ^" higher than it was while feeding the 
first rod, that is, it should be t 5 q" from rocker frame at base of 
pole. 

The feeding point of the D lamp is adjusted by sliding the 
clamp stop up or down, so that the rod will feed, when the rela- 
tive distances of the armature of the lifting magnet and the 
armature of the shunt magnet from rocker frame are in the ratio 
of 1 to 2. There should be a slight lateral play in the rocker, 
between the lugs of the rocker frame. 

Make a careful examination of all joints, screws, wires and 
other parts of the lamps. The armatures of all the magnets should 
be central with cores, and come down squarely and evenly. There 
should be a separation of -^~' between the silver contact points, 
when the armature of the starting magnet is down. This contact 
should be perfect when the armature is up. The arm for 
adjusting the tension should not touch the wire or frame of the 
lamp, when at the highest point. There should be a space of 
A" or i" between the body of the clutch and the arm of the 
clutch, to allow for wear on the bearing surfaces. 

Always trim the lamps with carbons of proper length to cut 
out automatically, that is, have twice as much carbon projecting 
from the top as from the bottom holder. Always allow a space 
of i" when the lamp is trimmed, from the round head screw in 
the rod, near the carbon holder, to the edge of upper bushing, so 
that there will be sufficient space to start the arc Be careful to 



156 HANDBOOK ON ENGINEERING. 

get the carbons as accurately centered as possible. They will 
generally come right after one or two trials. 

The arcs of the 1200 candle-power lamps should be adjusted 
to ¥ 3 T ", with full length of carbon. Arcs of 2000 candle-power 
lamps should be adjusted from t l" to -f~' when good carbons are 
used. Lamps should always maintain a fairly even arc. The 
length of the arc will slightly increase as the carbons burn away, 
but they should not hiss, flame, or overfeed at any time. If the 
switch is thrown and the lamp cutoff, and then turned on quickly, 
the upper carbon should " pick up " promptly with a normal arc, 
not hiss over a few seconds, and then burn as quietly as before. 

When the upper carbon rod is drawn up by the hand, the 
lamp should cut out promptly and not " flash " the generator. 
In the case the arc is very long or causes flashing, look at the 
contacts and see that they are clean and make a good square con- 
tact. Also examine the centering of the armature. The cause 
of the trouble will usually be found in one of these places. 

The action of a lamp that feeds badly may often be con- 
founded with that of a badly flaming carbon. The distinction 
can readily be made after a short observation. The arc of a lamp 
that feeds badly will gradually grow long until it flames, the 
clutch will let go suddenly, the upper carbon will fall until it 
touches the lower carbon, and then pick up. A bad carbon may 
burn nicely and feed evenly, until a bad spot in the carbon is 
reached, when the arc will suddenly become long and flame and 
smoke, due to impurities in the carbon. Instead of dropping as 
in the former case, the upper carbon will feed to its correct posi- 
tion, without touching the lower carbon. 

After the lamp has been tested and burns satisfactorily in the 
station, tighten up the adjusting screws, and if necessary, put a 
small amount of thick shellac on the bottom of the guide rod. 
This will prevent the step from falling, in case the screw which 
holds it becomes loose or broken. The lamps are now ready to 



HANDBOOK ON ENGINEERING. 157 

be placed on the circuit, but if it is necessary to store them, they 
should be put into some part of the building or engine room where 
they will not become covered with dust before they are taken out. 
If they become dusty, use a small hand bellows to blow away the 
dust which may have collected on the working parts of the lamps, 
before placing them on the circuit. 

SUMHARY. 

The following- summary of the foregoing instructions may be 
useful for the guidance of men in charge of dynamos : — 

1. In operating an arc system, attend strictly to all the points 
herein given. 

2. Be sure that the speed of the dynamo is right and that the 
belt has its proper tension. 

3. See that the regulator always works properly, and has suffi- 
cient " surplus " or space between its armature and the stop. 

4. Be careful that all connections of wires are well made. 

5. Do not allow the circuit to become uninsulated at any point. 

6. Keep every part of the machine and lamps scrupulously 
clean . 

7. Keep all the insulations free from metallic dust or gritty 
substances, by a careful cleaning once a day. 

8. Keep the bearings of the machine well supplied with the 
best quality of mineral oil. 

9. Do not use water or ice on a bearing in case of heating, as 
the water is liable to get into the armature and injure the insula- 
tion . 

10. Lubricate the commutator of the C and E machines bi 
touching the surface occasionally with an oiled cloth. 

11. The commutator on the machine is set carefully before 
leaving the factory in the best position for proper working, and 
its position marked by chisel marks on the commutator and shaft, 



158 HANDBOOK ON ENGINEERING. 

If the commutator is ever removed from the machine, it must be 
put back in exactly the same position on the shaft, and the red, 
white and blue leads must be put into the posts marked 1, 2 and 
3 respectively. If wrongly placed, the machine will either not 
generate, or will act very badly. 

12. When the commutator segments become badly worn, they 
may be turned down in a lathe, either by removing the commu- 
tator entirely from the shaft of the machine and putting it upon 
an arbor, or by removing the segments separately and screwing 
them to a jig, which may then be put into the lathe. The use of 
the jig is especially recommended for turning down the segments 
as the adjustment of the commutator is less liable to be changed 
than when the arbor is used. 

13. The durability of the commutator segments will depend on 
the care exercised in the running of the machine. 

14. The brushes must be set carefully by the "gauge for 
brushes," in the manner explained before. 

15. The spark on the tips of the brushes will vary with the set 
and wear of the brushes. It should be from i" to J" long, and 
only on the forward brushes. 

16. The carbon rods in every lamp should be carefully cleaned 
daily. 

17. The carbons should be in perfect alignment and firmly 
clamped in the holders. 

18. If a lamp burns badly and with a bluish flame, or contin- 
ually hisses, it is probably due to poor carbons, which should be 
removed and better ones substituted. 

19. The lamps rarely burn as well when first started as after- 
wards. This is principally due to the fact that the carbons 
require a little time to burn to the proper shape. 

20. The automatic regulator prevents the machine from gener- 
ating more than the amount of current required, so that the lamps 
may be thrown on or off the circuit at pleasure. 



HANDBOOK ON ENGINEERING. 



159 



21. Do not tamper with adjustments made in the factory. 

22. Do not imagine that every time a lamp hisses or flames a 
little it is out of adjustment. As a rule, bad working is due to 
stickiness of the moving parts, or to poor carbons. The lamps 
once properly adjusted and operated with good carbons, should 
not get out of adjustment, and should be let alone in that respect. 

23. If the machine works badly, it should be tested with a mag- 
neto for grounds of connection between the circuit and the frame 
of the machine. The circuit should also be daily tested, and any 
faults found should be immediately remedied, as otherwise they 
will inevitably cause trouble. 

24. All construction and repair work should be done in strict 
accordance with the rules herein laid down. 



TABLE OF MAGNETIZING FORCE IN AMPERE TURNS REQUIRED PER 
INCH OF LENGTH OF MAGNETIC CIRCUIT. 



Magnetic Den- 


MAGNETIZING FORCE IN AMPERE TURNS. 


sity per square 










inch in 










Gausses. 


Air. 


Cast Iron. 


Steel. 


Wrought Iron. 


5,000 


1,567 


3.80 


2.85 


1.50 


10,000 


3,134 


5.35 


4.25 


2.40 


15,000 


4,701' 


6.80 


5.35 


3.20 


20,000 


6,268 


8.00 


6.30 


3.90 


25,000 


7,835 


10.30 


7.50 


4.60 


30,000 


9,402 


16.20 


8.80 


5.30 


35,000 


10,969 


28.70 


10.20 


5.90 


40,000 


12,536 


49.00 


11.70 


6.50 


45,000 


14,103 


80.00 


13.40 


7.10 


50,000 


15,670 


160.00 


15.40 


8.20 


55,000 


17,237 


240.00 


17.80 


9.50 


60,000 


18,804 


350.00 


20.70 


11.00 


65,000 


20,371 


490.00 


24.10 


13.50 


70,000 


21,938 


650.00 


28.00 


17.00 


75,000 


23,505 
25,072 




34.00 


21.80 


80,000 




42.00 


27.50 









14 



160 HANDBOOK ON ENGINE EKING. 



CHAPTER Xa. 

Incandescent Wiring Table. 

Table on two following pages is arranged to enable wiremen to 
select the right sizes of wire for service connections and inside 
work. The figures at the top indicate distance in feet to center 
of distribution, in reality half the length of the circuit ; the four 
columns at the left showing the number of 16-candle power lamps 
at various voltages ; the other figures showing the sizes of wire, 
Brown & Sharpe gauge, to be used for distributing the number of 
lamps stated at the distances indicated and with the loss of 1 
volt. 

For example : To distribute 30 lamps of 110 volts at a dis- 
tance of 80 feet with a loss of 1 volt. In column of 110-volt 
lamps find the number 30, then follow the same line of figures to 
the right until the column headed 80 is reached, and it appears 
that No. 6 wire must be used. 

The same table may be used for other losses than 1 volt by 
dividing the given number of lamps by the number of volts to be 
lost, then with this product proceed as before in the table. 

For example : To distribute 30 lamps of 110 volts at a distance 
of 80 feet with a loss of 2 volts, divide 30 by 2 which gives 15, 
then find 15 in the column headed 110 volts and follow the same 
line of figures to the right until column headed 80 is reached, and 
it is found that No. 8 wire must be used. 

No wire smaller than No. 14 is shown in the table as the Na- 
tional Board of Fire Underwriters prohibits the use of a smaller 
size. Odd sizes smaller than No. 5 are not commercial and are 
therefore omitted. 



HANDBOOK ON ENGINEERING. 



161 



Incandescent Wiring Table. 

Sixteen Candle Power Lamps. Loss, One Volt. 

Table No. 1. Sizes of Wire are by B. & S. Gauge. 



52 Volt 

H 

Watt 


110 Volt 

Watt 
Lamps 


220 Volt 

4 

Watt 

Lamps 


550 Volt 

4 

Watt 

Lamps 


Distance in feet to center 
of Distribution. 


Lamps 


20' 

14 
14 
14 


25' 

14 
14 
14 


30' 

14 
14 
14 


37 

14 
14 
14 


40' 

14 
14 
14 


45' 


1 
2 
3 


2 

4 
6 


3 

7 

11 


9 
18 
28 


14 
14 
14 


4 
5 

6 


8 
10 
12 


15 
18 
22 


37 
46 
56 


14 

14 
14 


14 

14 
14 


14 
14 
14 


14 

14 
12 


14 
12 
12 


14 
12 

12 


7 
8 
9 


15 
17 
19 


26 
30 
33 


65 
74 
83 


14 
14 
14 


14 
12 

12 


12 
12 
12 


12 

12 
10 


12 
10 
10 


10 
10 
10 


10 
12 
14 


21 
25 
30 


37 
44 
52 


93 
111 
130 


12 
12 

12 


12 

10 
10 


12 
10 

10 


10 
10 
8 


10 

8 
8 


10 

8 
8 


16 
18 
20 


34 

38 
42 


59 

66 

74 


148 
167 

185 


10 
10 
10 


10 

8 
8 


8 
8 
8 


8 
8 
8 


8 
8 
6 


8 
6 
6 


25 
30 
35 


53 

63 

74 


92 
111 
130 


232 

278 
324 


8 
8 
6 


8 
6 
6 


6 
6 
6 


6 
6 
5 


6 
5 
5 


6 
5 
4 


40 
45 

- 50 


85 
95 
106 


148 
166 
185 


371 
428 
464 


6 
5 
5 


6 
5 
5 


6 
5 
4 


5 
4 
4 


4 

4 
3 


4 
3 
3 


55 

60 

65 


116 
127 
138 


203 
222 
240 


5L0 
557 
603 


4 
4 
3 


4 
4 
3 


4 
4 
3 


3 

3 
3 


3 
2 

2 


2 
2 

2 


70 
75 

80 


148 
159 
170 


260 
277 
296 


650 
696 

742 


3 

2 

2 


3 
2 
2 


3 

2 

2 


2 

2 

2 


2 

1 
1 


1 
1 
1 


90 
100 


191 
212 


333 
370 


835 
928 


1 
1 


1 
1 


1 
1 


1 
1 


1 








162 



HANDBOOK ON ENGINEERING. 



Incandescent Wiring Table. 

Sixteen Candle Power Lamps, Loss, One Volt. 
Table No. 1. Sizes of Wire are by B. & S. Gauge. 



DISTANCE IN FEET TO CENTER OF DISTRIBUTION. 



50' 


60' 


70' 


80' 


90' 


100' 


120' 


140' 


160' 


180' 


200' 


14 
14 
14 


14 
14 
14 


14 
14 
12 


14 
14 
12 


14 
14 
12 


14 
12 

10 


14 
12 
10 


14 
12 
10 


14 
10 

8 


14 
10 

8 


12 

10 
8 


12 
12 

10 


12 

10 
10 


12 

10 
10 


10 

10 

8 


10 

10 

8 


10 
8 
8 


8 
8 
8 


8 
8 
6 


8 
6 

6 


8 
6 
6 


6 
6 
6 


10 
10 

10 


10 
8 
8 


8 
8 
8 


8 
8 
8 


8 
8 
6 


8 
6 
6 


6 
6 
6 


6 
6 
5 


6 
5 
5 


5 
6 

4 


5 
4 
4 


8 
8 
8 


8 
8 
6 


8 
6 
6 


6 

6 
6 


6 
6 
5 


6 
5 
5 


5 
5 
4 


5 
4 
3 


4 
3 
3 


4 
3 
2 


3 

2 


6 
6 
6 


6 

6 
5 


6 
5 
5 


5 
5 

4 


5 
4 
4 


4 
4 
3 


3 
3 
2 


3 
2 
2 


2 
2 
1 


2 
1 
1 


1 

1 



5 

5 

4 


5 
4 
3 


4 
3 
2 


3 
2 
2 


3 
2 

1 


2 
1 


1 

1 



1 



00 





00 




00 
000 


00 

00 

000 


3 

3 

2 


2 
2 

1 


2 
1 

1 


1 




1 








00 


00 

00 

000 


00 
000 
000 


000 

000 

0000 


000 
0000 
0000 


0000 
0000 


2 
1 

1 


1 
1 











00 
00 


00 
00 
00 


00 
000 
000 


000 
000 

oooo 


0000 
0000 
0000 


0000 
0000 






1 








00 


00 
00 
00 


00 
000 
000 


000 
000 

000 


000 
0000 
0000 


0000 
0000 












00 


00 
000 


000 
000 


000 
0000 


0000 
0000 


0000 













HANDBOOK ON ENGINEERING. 



168 



Feet x 2 x 10.70. 



Table No. 2. 



Feet 




Feet 




Feet 




to end of 


Ft. x2xl0.70. 


to end of 


Ft.x2xl0.70. 


to end of 


Ft.x2xl0.70. 


Circuit. 




Circuit. 




Circuit. 




5 


107 


185 


3,959 


365 


7,811 


10 


214 


190 


4,066 


370 


7,918 


15 


321 


195 


4,173 


375 


8,025 


20 


428 


200 


4,280 


380 


8,132 


25 


535 


205 


4,387 


385 


8,239 


30 


642 


210 


4,494 


390 


8,346 


35 


749 


215 


4,601 


895 


8,453 


40 


856 


220 


4,708 


400 


8,560 


45 


963 


225 


4,815 


405 


8,667 


50 


1,070 


230 


4,922 


410 


8,774 


55 


1,177 


235 


5,029 


415 


8,881 


60 


1,284 


240 


5,136 


420 


8,988 


65 


1,391 


245 


5,243 


425 


9,095 


70 


1,498 


250 


5,350 


430 


9,202 


75 


1,605 


255 


5,457 


435 


9,309 


80 


1,712 


260 


5,564 


440 


9,416 


85 


1,819 


265 


5,671 


445 


9,523 


90 


1,926 


270 


5,778 


450 


9,630 


95 


2,033 


275 


5,885 


455 


9,737 


100 


2,140 


280 


5,992 


460 


9,844 


105 


2,247 


285 


6,099 


465 


9,951 


110 


2,354 


290 


6,206 


470 


10,058 


115 


2,461 


295 


6,313 


475 


10,165 


120 


2,568 


300 


6,420 


480 


10,272 


125 


2,675 


305 


6,527 


485 


10,379 


130 


2,782 


310 


6,634 


490 


10,486 


135 


2,889 


315 


6,741 


495 


10,593 


140 


2,996 


320 


6,848 


500 


10,700 


145 


3,103 


325 


6,955 


510 


10,914 


150 


3,210 


330 


7,062 


520 


11,128 


155 


3,317 


335 


7,169 


530 


11,342 


160 


3,424 


340 


7,276 


540 


11,556 


165 


3,531 


345 


7,383 


550 


11,770 


170 


3,638 


350 


' 7,490 


560 


11,984 


175 


3,745 


355 


7,597 


570 


12,198 


180 


3,852 


360 


7,704 


580 


12,412 



164 



HANDBQQK ON ENGINEERING. 



Table No. 2. 



Feetx2x 10.70. 



Feet 




Feet 




Feet 




to end of 


Ft. x2xl0.70. 


to end of 


Ft.x2xl0.70 


to end of 


Ft.x2xl0.70. 


Circuit. 




Circuit. 




Circuit. 




590 


12,626 


970 


20,758 


1,350 


28,890 


600 


12,840 


980 


20,972 


1,360 


29,104 


610 


13,054 


900 


21,186 


1,370 


29,318 


620 


13,268 


1,000 


21,400 


1,380 


29,532 


630 


13,482 


1,010 


21,614 


1,390 


29,746 


640 


13,696 


1,020 


21,828 


1,400 


29,960 


650 


13,910 


1,030 


22,042 


1,410 


30,174 


660 


14,124 


1,040 


22,256 


1,420 


30,388 


670 


14,338 


1,050 


22,470 


1,430 


30,602 


680 


14,552 


1,060 


22,684 


1,440 


30,816 


690 


14,766 


1,070 


22,898 


1,450 


31,030 


700 


14,980 


1,080 


23,112 


1,460 


31,244 


710 


15,194 


1,090 


23,326 


1,470 


31,458 


720 


15,408 


1,100 


23,540 


1,480 


31,672 


730 


15,622 


1,110 


23,754 


1,490 


31,886 


740 


15,836 


1,120 


23,968 


1,500 


32,100 


750 


16,050 


1,130 


24,182 


1,510 


32,314 


760 


16,264 


1,140 


24,396 


1,520 


32,528 


770 


16,478 


1,150 


24,610 


1,530 


32,742 


780 


16,692 


1,160 


24,824 


1 540 


32,956 


790 


16,906 


1,170 


25,038 


1,550 


33,170 


800 


17,120 


1,180 


25,252 


1,560 


33,384 


810 


17,334 


1,190 


25,466 


1,570 


33,598 


820 


17,548 


1,200 


25,680 


1,580 


33,812 


830 


17.762 


1,210 


25,894 


1,590 


34,026 


840 


17,976 


1,220 


26,108 


1,600 


34,240 


850 


18,190 


1,230 


26,322 


1,610 


34,454 


860 


18,404 


1,240 


26,536 


1,620 


34,668 


870 


18,618 


1,250 


26,750 


1,630 


34,882 


880 


18,832 


1,260 


26,964 


1,640 


35,096 


890 


19,046 


1,270 


27,178 


1,650 


35,310 


900 


19,260 


1,280 


27,392 


1,660 


35,524 


910 


19,474 


1,290 


27,606 


1,670 


35,738 


920 


19,688 


1,300 


27,820 


1,680 


35,952 


930 


19,902 


1,310 


28,034 


1,690 


36,166 


940 


20,116 


1,320 


28,248 


1,700 


36,380 


950 


20,330 


1.330 


28,462 


1,710 


36,594 


960 


20,544 


1,340 


28,676 


1,720 


36,808 



HANDBOOK ON ENGINEERING. 



165 



Table No. 2. 



Feetx 2x10.70. 



Feet 




Feet 




Feet 




to end of 


Ft.x2xl0.70. 


to end of 


Ft.x2xl0.70. 


to end of 


Ft.x2xl0.70. 


Circuit. 




Circuit. 




Circuit. 




1,730 


37,022 


2,450 


52,430 


4,250 


90,950 


1,740 


37,236 


2,500 


53,500 


4,300 


92,020 


1,750 


37,450 


2,550 


54,570 


4 350 


93 090 


1,760 


37,664 


2,600 


55,640 


4,400 


94,160 


1,770 


37,878 


2,650 


56,710 


4,450 


95,230 


1,780 


38,092 


2,700 


57,780 


4,500 


96 300 


1,790 


38,306 


2,750 


58,850 


4,550 


97,370 


1,800 


38,520 


2,800 


59,920 


4,600 


98,440 


1,810 


38,734 


2,850 


60,990 


4,650 


99,510 


1,820 


38,948 


2,900 


• 62,060 


4,700 


100,580 


1,830 


39,162 


2,950 


63,130 


4,750 


101,650 


1,840 


39,376 


3,000 


64,200 


4,800 


102,720 


1,850 


39.590 


3,050 


65,270 


4,850 


103,790 


1,860 


39,804 


3,100 


66,340 


4,900 


104,860 


1,870 


40 018 


3,150 


67,410 


4,950 


105,930 


1,880 


40,232 


■ 3,200 


68,480 


5,000 


107,000 


1,890 


40,446 


3,250 


69,550 


5,050 


108,070 


1,900 


40,660 


3,300 


70,620 


5,100 


109,140 


1,910 


40,874 


3,350 


71,690 


5,150 


110,210 


1,920 


41,088 


3,400 


72,760 


5,200 


111,280 


1,930 


41,302 


3,450 


73,830 


5,250 


112,350 


1,940 


41,516 


3,500 


74,900 


5,300 


113,420 


1,950 


41,730 


3,550 


75,970 


5,350 


114,400 


1,960 


41,944 


3,600 


77,040 


5,400 


115,560 


1,970 


42,158 


3,650 


78,110 


5,450 


116,630 


1,980 


42,372 


3,700 


79,180 


5,500 


117,700 


1,990 


42,586 


3,750 


80,250 


5,550 


118,770 


2,000 


42,800 


3,800 


81,320 


5,600 


119,840 


2,050 


43,870 


3,850 


82,390 


5,650 


120,910 


2,100 


44,940 


3,900 


83,460 


5,700 


121,980 


2,150 


46,010 


3.950 


84,530 


. 5,750 


123,050 


2/200 


47,080 


4',000 


85,600 


5,800 


124,120 


2,250 


48,150 


4,050 


86,670 


5,850 


125,190 


2,300 


49,220 


4,100 


87,740 


5,900 


126,260 


2,350 


50,290 


4,150 


88,810 


5,950 


127,330 


2,400 


51,360 


4,200 


89,880 


6,000 


128,400 



166 



Table No. 2. 



HANDBOOK ON ENGINEERING. 

Feet x 2 x 10.70. 



Miles. 


Ft.x2xl0.70 


Miles. 


Ft.x2xl0.70 


Miles. 


Ft.x2xl0.70. 


h 


564,960 


4 


451,968 


n 


847,440 


1 


112,992 


H 


508,464 


8 


903,936 


n 


169,488 


5 


564,960 


H 


960,432 


2 


225,984 


5h 


621,456 


9 


1,016,928 


n 


282,480 


6 


677,952 


H 


1,073,424 


3 


338,976 


Gh 


734,448 


10 


1,129,920 


H 


395,472 


7 


790,944 







(A) 
(B) 
(C) 



Feet x 2 x 10.7 x Amperes 

Volts lost 
Feet x 2 x 10.7 x Amperes 

Circular mils. 
Circular mills x volts lost 



= Circular mils. 



: VoltS lost. 



= Amperes. 



Feetx 2 x 10.7 

In calculating the sizes of wire as shown in the Incandescent 
Wiring Table a formula (A) has been used in which there is a 
constant 10.7, the number of circular mils in a copper wire which 
would have a resistance of one ohm for one foot of length. One 
ampere through one ohm resistance loses one volt. To determine 
the size of wire necessary for carrying a given current a given 
distance in feet, multiply the number of feet by 2 to obtain the 
actual length of circuit, multiply this product by the constant 
10.7 and it will give the circular mils necessary for one ohm re- 
sistance, multiply this by the amperes and it gives the circular 
mils necessary for the loss of one volt. Divide this last result 
by the volts lost and it gives the circular mils necessary. Hence 
the formula "A." 

By simply transposing the terms we obtain formula " B," which 
can be used to determine the volts lost in a given length of wire 
of certain size carrying a certain number of amperes. 



HANDBOOK ON ENGINEERING. 167 

Again, by another change in the terms, we obtain formula 
"C," which shows- the number of amperes which a wire of given 
size and length will carry at a given number of volts lost. 

Table No. 2 has been arranged for the purpose of saving time 
in the use of these formulae. It shows the result of Feet x 2 x 
10.7 for various distances over which it may be desired to trans- 
mit current. 

A few examples will assist in showing the use of the formulas 
and tables. 

Suppose we wish to distribute 300 16 c. p. 3.5 watt lamps of 
110 volts at a distance of 490 feet with a loss of 10 per cent. 
Using formula A, 

490 feet x 2 x 10.7 (find it in table No. 2) = 10486. 
300 lamps of 110 volts = 152.7 amperes. 
(See table No. 3 for amperes per lamp, and multiply by 300.) 
10 per cent loss on 110 volt system = 12.22 volts. (See 

table No. 4.) 
10486 x 152.7 amperes = 1601212 cire. mils. -^ 12.22 volts 
lost= 131032 circ. mils. 
In our table it shows the size of wire for this number of circ. 
mils, to be 00. 

To check this and determine exactly the volts lost in this cir- 
cuit by using No. 00 wire, use formula B, as follows: 

10,486 x 152.7 amperes = 1601212 ~ 133079 circ. mils. == 
12.03 volts lost. 

Suppose it is desired to distribute 1,000 lamps at a distance of 
1950 feet by 3-wire system, viz., 220 volts, with a loss of 10 per 
cent. 

Using formula A, 

1950 feet x 2 x 10.7 (see table) — 41730. 
1000 lamps on 220 volt system = 291 amperes. 
(See table No. 5 for amperes per lamp, and multiply by 
1000.) 



168 HANDBOOK ON ENGINEERING. 

10 per cent on 220 volt system = 24.44 volts lost. (See 

table No. 4.) 
41730 x 291 amperes = 12143430 -f- 24.44 volts lost 

= 496867 circ. mils. 
500000 circ. mils, the nearest commercial size, should be 
used. 
Check this as before by formula B. 

41730 x 291 amperes = 12143430-*- 500000 circ. mils 
= 24.29 volts lost. 
Suppose we wish to deliver 100 h. p. to a 500 volt motor, at 
a distance of 4850 feet with 10 per cent loss : 
Again using formula A, 

4850 feet x 2 x 10.7 = L03790. 

100 h. p. at 500 volts = 160 amperes. (See table No. 3.) 
10 per cent loss on 500 volts system = 55. 5 volts. (See 
table No. 4.) 
■ 103790 x 160 amperes = 16606400 -=-55.5 volts = 299215 
circ. mils. 
300000 circ. mils, cable should be used. 
Check this as before by formula B. 

103790 x 160 amperes = 16606400 -*- 300000 circ. mils 
= 55.35 volts lost. 
To ascertain how many amperes could be carried to a distance 
of 4850 feet with 500 volts with 10 per cent loss, use formula C : 
4850 feet x 2 x 10.7 = 103790. 
10 per cent loss on 500 volts system = 55.5 volts. 
300000 circ. mils x 55.5 volts lost -~- 103790 = 160.42 am- 
peres, which as will appear by reference to table No. 3, 
will permit the use of 100 h. p. motor. 



HANDBOOK ON ENGINEERING. 



169 



Amperes per Motor. 



Table No. 3. 











VOLTS. 




II. p. 


Per Cent 
, Efficiency 


Watts. 




















110 


115 


120 


1 


65 


860 


7.82 


7.48 


7.17 


1 


65 


1148 


10.4 


9.98 


9.57 


2 


65 


2295 


20.8 


20 


19.1 


?h 


75 


2487 


22 6 


21.6 


20.7 


u 


75 


3480 


31.6 


30.3 


29.0 


5 


80 


4662 


42 4 


40.5 


388 


74 


80 


6994 


63 6 


60.8 


58.3 


10 


85 


8776 


79.8 


76.3 


73.1 


15 


85 


13165 


120. 


114. 


• 110. 


20 


90 


16578 


151. 


144. 


138. 


25 


90 


20722 


188. 


180. 


173. 


30 


90 


24867 


226, 


216. 


207. 


40 


90 


33155 


301. 


288. 


276. 


50 


90 


41444 


377. 


360. 


345. 


70 


90 


58022 


528. 


505. 


484. 


90 


90 


74600 


678. 


649. 


622. 


100 


93 


80215 


729. 


697. 


668. 


125 


93 


1002(i9 


912. 


872. 


836. 


150 


93 


120323 


1094. 


1046. 


1003. 



The above table is arranged to show the amperes per motor at dif- 
ferent voltages for several sizes of motors at efficiencies obtained in 
ordinary practice 



170 



HANDBOOK ON ENGINEERING. 



Table No. 8. 



Amperes per Motor. 



125 


220 


250 


500 


525 


550 


6.88 


3.91 


3.44 


1.72 


1.64 


1.56 


9.18 


5.22 


4.59 


2.30 


2.19 


2.09 


18.4 


10.4 


9.18 


4.59 


4.37 


4.17 


19.9 


11.3 


9.95 


4.97 


4.74 


4.52 


27.8 


15.8 


13.9 


6.96 


6.63 


6.33 


37.3 


21.2 


18.6 


9.32 


8.88 


8.48 


56.0 


31.8 


28.0 


14.0 


13.3 


12.7 


70.2 


39.9 


35.1 


17.6 


16.7 


16.0 


105. 


59.8 


52.6 


26.3 


25.1 


23.9 


133. 


75.4 


66.3 


33.2 


31.6 


30.1 


166. 


94.2 


82.9 


41.4 


39.5 


37.7 


199. 


113. 


99.4 


49.7 


47.4 


45.2 


265. 


151. 


133. 


66.3 


63.2 


60.3 


332. 


188. 


166. 


82.9 


79.0 


75.4 


464. 


264. 


232. 


116. 


111. 


106. 


597. 


339. 


298. 


149. 


142. 


136. 


642. 


365. 


321. 


160. 


153. 


146. 


802. 


456. 


401. 


200. 


191. 


182. 


963. 


547. 


481. 


241. 


229. 


219. 



The above table is arranged to show the amperes per motor at 
different voltages for several sizes of motors at efficiencies obtained in 
ordinary practice* 



HANDBOOK ON ENGINEERING. 



171 



Volts Lost at Different Per Cent Drop. 

Voltage at Lamp or Distribution Point, Top Row. 
Table No. 4. 



Volts 


52 


75 


1C0 


110 


220 


400 


h% 


.261 


.376 


.502 


.552 


1.10 


2.01 


1% 


.525 


.757 


1.01 


1.11 


2.22 


4.04 


H% 


.787 


1-14 


1.52 


1.67 


3.35 


6.09 


2% 


1.06 


1.53 


2.04 


2.24 


4.48 


8.16 


n% 


1.33 


1.92 


2.56 


2.82 


5.64 


10.25 


3% 


1.61 


2.31 


3.09 


3.40 


6.80 


12.37 


4% 


2.16 


3.12 


4.16 


4.58 


9.16 


16.06 


5% 


2.73 


3.94 


5.26 


5.78 


11.57 


21.05 


6% 


3.31 


4.78 


6.38 


7.02 


14.04 


25.53 


7% 


3.91 


5.G4 


7.52 


8.27 


16.55 


30.10 


8% 


4.52 


6 = 52 


8.69 


9.56 


19.13 


34.78 


9% 


5.14. 


7°41 


9.89 


10.87 


21.75 


39.56 


10% 


5.77 


8o33 


11.11 


12.22 


24.44 


44.44 


12% 


7.09 


10.22 


13.63 


14»99 


29.99 


54.54 


13% 


7.76 


11.10 


14.94 


16.43 


32.87 


59.76 


14% 


8.46 


12.20 


16.27 


17.90 


35.81 


65.1 


15% 


9.17 


13.23 


17.64 


19.41 


38.82 


70.5 


20% 


13. 


18.75 


25. 


27.50 


55. 


100. 


25% 


17.33 


25. 


33.33 


36.66 


73.33 


133. 



The above table shows the loss in voltage between dynamos and 
distribution point at different per cents and for various voltages. 



172 



HANDBOOK ON ENGINEERING. 



Volts Lost at Different Per Cent Drop. 

Voltage at Lamp or Distribution Point, Top Row. 
Table No. 4. 



500 


600 


800 


1000 


1200 


2000 


2.51 


3 01 


4.02 


5 02 


6.03 


10.05 


5 05 


6.66 


8.08 


10.10 


12.12 


20.2 


7.61 


9.13 


12.1 


15 2 


18.2 


30.4 


10 2 


12.2 


16.3 


20 4 


24.4 


40.8 


12 8 


15 3 


20.5 


25.6 


30.7 


51.2 


15.4 


18.5 


24.7 


30.9 


37.1 


61.8 


20.8 


24.9 


33.3 


41.6 


49 9 


83.3 


26.3 


31.5 


42.1 


52.6 


63.1 


105. 


31.9 


38.2 


51. 


63.8 


76.5 


127. 


37.6 


45.1 


60.2 


75 2 


90.3 


150. 


43.4 


52.1 


69.5 


86.9 


104. 


173. 


49.4 


59.3 


79.1 


98.9 


118. 


197. 


55 5 


66.6 


88.8 


111. 


133. 


222. 


61.7 


74.1 


98.8 


123. 


148. 


247. 


68.1 


81.8 


109. 


136. 


163. 


272. 


74.7 


89.6 


119. 


149. 


179. 


298. 


81.3 


97.6 


130. 


162. 


195. 


325. 


88.2 


105. 


141. 


176. 


211. 


352. 


125. 


150. 


200. 


250. 


300. 


400. 


166. 


200. 


266. 


333. 


400. 


6U6. 



By adding the volts given in the table to the voltage at motor or lamp 
the result shows the voltage necessary at dynamo for voltage required 
at point of distribution. 



HANDBOOK ON ENGINEERING. 



173 



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174 



HANDBOOK ON ENGINEERING, 



Approximate Weight and Measurement of " 0. K. 
Weatherproof Copper Wire. 

Table No. 6. 



Triple Braided 



B. & S. 


Feet 


Pounds 


Pounds 


Gauge No. 


per Pound. 


per 1000 ft. 


Per Mile. 


0000 


1.30 


767 


4050 


000 


1.59 


629 


3320 


00 


2.02 


495 


2610 





2.45 


407 


2150 


1 


3.22 


310 


1640 


2 


4.00 


250 


1320 


3 


5.03 


199 


1050 


4 


6.10 


164 


865 


5 


7.43 


135 


710 


6 


9.00 


111 


587 


8 


13.54 


74 


390 


10 


18,85 


53 


280 


12 


28.54 


35 


185 


14 


40.61 


25 


130 


16 


60.00 


17 


88 


18 


75.43 


13 


70 



HANDBOOK ON ENGINEERING. 



175 



Table Showing Difference Between Wire Gauges in Decimal Parts 

Table No. 7. of an Inch. 





u 

*** 
as a a 


© 

1 


V f-n si 

° c2 

51 i 
sis 


6 . 

u - 

M 


K 


O OQ 





6® 


l^co 


S - 


.a a r 00 


3 a 


1 


hS 





S3 


<J 


U'Jl 




2 EH 


fc 


^2 


fc 


000000 






.46 
.43 
.393 
.362 
.331 

.307 
.283 
.263 
.244 
.225 

.207 








000000 


00000 






"■.'45"'" 

.4 

.36 

.33 

.305 

.285 

.265 

.245 

.225 

.205 






00000 


0000 


.."."46*"" 

.40964 
.3648 

.32495 
.2893 
.25763 
22942 
.20431 
.18194 


""'!454 
.425 

.38 

.34 
.3 

.284 
.259 
.238 

.22 


'"".i 

.372 

.348 

.324 

.3 

.276 

.252 

.232 

.212 




0000 


000 




000 


00 




00 










1 




1 


2 




2 


3 




3 


4 




4 


5 




5 


6 


.16202 

.14428 
. 12849 


.203 
.18 
.165 


.192 
.177 
.162 


.19 
.175 

.16 


.192 
.176 
.16 




6 


7 




7 


8 




8 


9 


.11443 


.118 


.148 


.145 


.144 




9 


10 


.10189 

.090742 


.134 
.12 


.135 
.12 


.13 
.1175 


.128 
.116 




10 


11 




11 


12 


.08US08 
.071961 
.064084 


.K,9 
095 
.083 


.105 
.092 
.08 


.105 

.0925 
.08 


.104 
.092 
.08 




12 


13 




13 


14 


083'" 


14 


15 


.057068 


.072 


.072 


.07 


.072 


.072 


15 


16 


.05082 


.065 


.063 


.061 


.064 


.065 


16 


17 


.045257 


.058 


.054 


.0525 


.056 


.058 


17 


18 


.040303 


.049 


.047 


.045 


.048 


.049 


18 


19 


.03589 


.042 


.041 


.039 


.04 


.04 


19 


20 


.031961 


.035 


.035 


.034 


.036 


.035 


20 


21 


.028462 


.032 


.032 


.03 


.032 


0315 


21 


22 


.025347 


.028 


.028 


.27 


.028 


.0295 


22 


23 


.022571 


.025 


.025 


.024 


.024 


.027 


23 


24 


.0201 


.022 


.023 


.0215 


.022 


.025 


24 


25 


.0179 


.02 


.02 


.019 


.02 


.023 


25 


26 


.01594 


.018 


.018 


.018 


.013 


.0205 


26 


27 


.014195 


.016 


.017 


.017 


.0164 


.01875 


27 


28 


.012641 


.014 


.016 


.016 


.0148 


.0165 


28 


29 


.011257 


.013 


.015 


.015 


.0136 


.0155 


29 


30 


.010025 


.012 


.014 


.014 


.0124 


.01375 


30 


31 


.008928 


.01 


.0135 


.013 


.0116 


.01225 


31 


32 


.00795 


.009 


.013 


.012 


.0108 


.01125 


32 


33 


.00708 


.008 


Oil 


.011 


.01 


.01025 


33 


34 


.006304 


.007 


.01 


.01 


.0092 


.0095 


34 


35 


.005614 


.005 


.0095 


.009 


.0084 


.009 


35 


36 


.005 


.004 


.009 


.008 


.0076 


.0075 


36 


37 


.004453 
. C03%5 
.003531 
.003144 




.0085 
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.0075 

.007 


.00725 
.0065 
.00575 

.005 


.0068 
.006 
.0052 
.0048 


.0065 
.00575 
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0045 


37 


38 




38 


39 




39 


40 




40 









176 



HANDBOOK ON ENGINEERING. 



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HANDBOOK ON ENGINEERING. 177 

THE STEAM ENGINE. 

CHAPTER XI. 
THE SELECTION OF AN ENGINE. 

There are so many conflicting statements in regard to the 
merits and demerits of the several engines placed in the market 
that one is often confused in judgment, and scarcely knows how 
to proceed in the matter of selection, 

It is easy to advise that " When you are ready to buy, select 
the best engine, for in the long run the best is the cheapest." 
No one would pretend to deny this as a general rule, yet there are 
circumstances which so materially modify this rule that it would 
seem to a casual observer to be entirely set aside. There are 
localities in which the price of fuel is so low that it scarcely war- 
rants the doubling of the price on an engine to save it ; and in 
such localities the owners usually want an engine of the very 
simplest construction ; hence, they almost invariably select an 
ordinary slide valve engine with a throttling governor. This 
selection is made for several reasons, among which are low first 
cost, simple in detail, remoteness from the manufacturer or from 
repair shops. 

For small powers in which it is desirable that the investment 
be as low as consistent with commercial success, the engine 
selected should be fitted with a common slide valve ; this will in 
general apply to all engines having cylinders eight inches or less 
in diameter. 

If upon a thorough canvass of the situation, it then be thought 
advisable to employ an automatic cut-off engine, the next ques- 
tion would probably be whether it shall be fitted with a positive, 
or some one of the various ' ' drop ' ' movements now in the 
market. 

12 



178 HANDBOOK ON ENGINEERING. 

For the smaller sizes, say 8 to 24 inches diameter of cylinder, 
it will perhaps he found more desirable to use an automatic slide 
cut-off, of which there are now several varieties offered through 
the trade. This style of engine has the advantage of being low- 
priced, efficient and economical. 

Small engines are usually required to run at pretty high 
speed ; there is a very decided advantage in this on the score of 
economy, as a small engine running at a quick speed will be quite 
as efficient as a large engine running at a slow speed, with the 
further advantage that the former will not cost in original outlay 
more than about two-thirds of the latter, while the cost of operat- 
ing will be no greater per indicated horse jjower. 

The slide valve is still used to the almost total exclusion of all 
other kinds in locomotives. It is doubtful whether a better valve 
for that particular use can be devised. It is simple, efficient, and 
readily obeys the action of the link when controlled or adjusted 
by the engineer. For portable engines and the smaller stationary 
engines it leaves little to be desired in point of simplicity. 

One objection to a slide valve is that it cannot readily be made 
to cut off steam at, say, half-stroke or less, without interfering 
with the exhaust. In ordinary practice | to f seems to be where 
most slide valves cut off as a minimum, perhaps f would repre- 
sent nearer the actual average conditions. 

It can easily be shown that this is very wasteful of steam, and 
consequently not economical in fuel ; but as there are cases in 
which the loss in fuel is fully gained by other advantages, the 
ordinary slide valve will, in all probability, continue to be 
used. 

High speed engines. — The general tendency seems now to be 
in the direction of a horizontal engine with a stroke of medium 
length having a rapid piston speed and a rapid rotation of crank 
shaft, rather than a longer stroke with a less rate of revolution. 
This rapid movement of piston and crank shaft permits the use of 



HANDBOOK ON ENGINEERING. 179 

small fly-wheels and driving pulleys, and thus very materially 
reduces the cost of an engine for a given power. 

To illustrate this, it may be said that a 1(3 x 48 inch engine 
using steam at 80 lbs. pressure and cutting off J stroke, running 
at the rate of 60 revolutions per minute, may be replaced by 
an engine having a 13 x 24 inch cylinder, running at the rate of 
200 strokes per minute, the pressure of steam and point of cut- 
ting off remaining the same, both engines being non-condensing, 
and representing the best examples of their kind. The differ- 
ence between 60 and 200 revolutions per minute in millwright 
work is very great, but there is a constantly growing demand for 
an engine which shall meet such a requirement whenever it 
shall present itself ; by this is not to be understood an engine 
which shall be used at either speed indiscriminately, but rather a 
type of engine which shall be economical in fuel, and shall be of 
a kind by which the rate of revolution may be such as to suit the 
millwright's work without loss of economy in working, and with- 
out excessive outlay for the engine itself in proportion to power 
developed. 

Slow speed engines are designed and built from a standpoint 
entirely different from that of high speed engines ; in the former 
case the reciprocating parts are made as light as possible, con- 
sistent with safety. The fly wheel is large in diameter and made 
with a very heavy rim, especially is this the case with auto- 
matic cut-off engines of long stroke and slow revolution of crank 
shaft. 

In high speed engines the reciprocating parts are often of great 
weight, in order to insure the utmost smoothness of running. 
The piston and cross-head are made of unusual weight that at the 
beginning of the stroke they may require a large part of the steam 
pressure to set them in motion ; this absorbing of power at the 
beginning of the stroke is for the purpose of temporarily storing 
it up in the reciprocating parts that it may be given off at the 



180 



HANDBOOK ON ENGINEERING. 



later portions of the stroke, by imparting their momentum to the 
crank ; thus at the beginning of the stroke, these reciprocating 
parts act as a temporary resistance, but once in motion they tend 
by their inertia to equalize the pressure on the crank pin, and so 
produce not only smooth running, but a very uniform motion. 

Results to be obtained in practice. — The best automatic non- 
condensing engines furnish an indicated horse power for about 
three pounds of good coal, depending somewhat upon the fitness 
of the engine for the work and the quality of the coal. With a 
condenser attached, a consumption as low as two pounds has been 
reported, but this is an exceptional result, 2 \ pounds may be 
quoted as good practice. The larger the engine the better the 
showing, as compared with smaller engines. 

For ordinary slide valve engines, the coal burned per indicated 
horse power will vary from 9 to 12 lbs., for the sake of illustra- 
tion, we will say 10 lbs., and that the engine is of such size as 
would require for a year's run $3,000 worth of coal ; now, an 
ordinary adjustable cut-off engine with throttling governor, ought 
to save at least half that amount of coal, or say $1,500 per year ; 
if the best automatic engine were employed using 2| lbs. of coal 
per horse power, a further saving of $750 per year could be 
effected, or between the two extremes $2,250 per year in saving 
of coal, without interfering in any way with the power, with the 
exception, perhaps, that the automatic engine will furnish abetter 
power than the former engine. It is easy to see that it is true 
economy to buy the best engine and pay the extra cost of con- 
struction, if the saving of fuel is an element entering into the 
question of selection. 

The cost of an engine for any particular service is always to 
be taken into consideration, for it is possible to contract for a 
certain saving of coal at too high a price, not simply when paid 
out as the original purchase money, but with this economy of 
fuel, the purchaser may have many vexatious and damaging 



HANDBOOK ON ENGINEERING. 181 

delays caused by the breaking of the automatic mechanism of the 
engine. All such delays which would not have occurred to an 
ordinary or simpler engine, are to be charged against any saving 
credited to the engine which failed in producing a regular and 
constant power. Take a flouring mill for example, producing 400 
barrels per day ; it is easy to see how a single day's stoppage 
would interfere with the trade and shipment by the proprieters, 
yet it would require a very small break in an engine that would 
require less than a day for repairs. 

This does not argue against high grade engines, but the pur- 
chaser should be certain that the engine when once on its founda- 
tions shall be as free from dangers of this kind as any other 
engine of similar economy. 

There are engines which from their peculiar construction 
appear to be very complex, and this objection is often urged 
against them, while the fact is the complexity is apparent rather 
than real. Take the Corliss engine, for example; it is doubtful 
whether there is another automatic cut-off engine in successful 
use in this or any other country which has cost less for repairs 
during the last ten or twenty years. It is true it contains a great 
many separate pieces in the valve mechanism, but the pieces 
themselves are simple, durable, easily accessible and always in 
sight. These several parts are not liable to excessive wear, but 
such as there is can be readily adjusted. 

The engines to be preferred are those in which the valve 
adjusting mechanism is outside of the steam chest and which is in 
plain sight at all times when the engine is in motion. 

Location of engine. — This will depend upon circumstances, 
but it is far from true economy to place an engine in a dark cellar, 
or in some inconvenient place above ground. The engine as the 
prime mover, should have all the care and attention which may be 
needed to insure regular and efficient working. 

Machinery in the dark is almost sure to be neglected. If the 



182 HANDBOOK ON ENGINEERING. 

design of the building, or the nature of the business, is such that 
the engine must be located underground, there should be some 
provision for letting in the daylight ; the extra expense incurred 
will soon be saved by the order, cleanliness and fewer repairs 
required, following neglect. 

The engine should always be close to, but not in the boiler 
room. Many a high-priced engine has had its days of usefulness 
shortened by the abrasive action of fine ashes and coal dust 
coming in contact with the wearing surfaces. There should always 
be a wall or tight partition between the engine and fire room. 

The foundations for an engine should be large and deep. 
Too many manufacturers in marking dimensions of foundation 
drawings for engines, make them altogether too shallow. The 
stability of an engine depends more on the depth than on the 
breadth of the foundations. Stone should be used for founda- 
tions rather than brick, but if the latter must be used they should 
be hard burned and laid in a good cement rather than a lime 
mortar. If the bottom of the pit dug for the engine foundation 
be wet, or the soil uncertain in its stability, it is a good plan to 
make a solid concrete block about a foot and a half thick, on 
which the foundation may be continued to the top. If such a 
concrete block be made with the right kind of cement it will be 
almost as hard and solid as a whole stone. 

The most economical engine is the one in which high pressure 
steam can be used during such portion of the stroke as may be 
necessary, then quickly cut off by a valve which shall not inter- 
fere with the exhaust at the opposite end of the cylinder, and 
allow the steam to expand in the cylinder to a pressure which 
shall not fall below that necessary to overcome the back pressure 
on the piston. In general, the most successful cut-off engines 
use the boiler pressure for a distance of one-fifth to three-eighths 
of the stroke from the beginning ; at this point the steam is cut 
off and allowed to expand throughout the balance of the stroke. 



HANDBOOK ON ENGINEERING. 



183 



The gain by expansion consists in the admission of steam at a 
pressure much above the average required to do the work, and 
allowing it to follow but a small portion of the stroke, then ex- 
panding to a lower than the average pressure at the end of the 
stroke, The mean effective pressure on the piston is that by 
which the power of the engine is measured ; hence, it follows that 
the higher economy is to be reached, other things being equal, where 
the mean effective pressure on the piston is highest when com- 
pared with the terminal pressure, or the pressure at the end of the 
stroke. In order to get this, a high initial pressure is used ; the 
steam follows as short a distance as possible to keep the motion 
regular under a load, and then expanding down to as near the 
atmospheric pressure as possible. 

The following table exhibits at a glance the performance of a 
non-condensing eDgine cutting off at different portions of the 
stroke. The initial pressure of steam being in each case eighty 
pounds per square inch. 

CUT-OFF IN PARTS OF THE STROKE. 



Mean effective pressure . 

Terminal pressure . 

Pounds water per h'r per 
H. P 



1 

10 


2 
10 


3 

10 


4 
10 


18 


35 


48 


57 


11 


20 


30 


39 


20 


21 


22 


23 



_5_ 
10 



6& 

48 

25 



Fractions are omitted in the above table and the nearest whole 
number given. 

Governor* — Any automatic device by which the speed of an 
engine is controlled may properly be called a governor. There 



184 HANDBOOK ON ENGINEERING. 

are now two distinct methods by which the steam supplied to an 
engine is thus brought under control. The first is usually applied 
to slide valve engines having a fixed cut-off, and consists in the 
adjustment of a valve by which the pressure of steam in the 
cylinder is increased or diminished in order to maintain a con- 
stant rate of revolution with a variable load. The second device 
consists in a mechanism by which the whole boiler pressure is 
admitted to the cylinder, which is allowed to follow the piston to 
such portion of the stroke as will maintain a regular rate of revo- 
lution ; the steam is then suddenly cut off at each half revolution 
of the engine, thus furnishing a greater or less volume of steam at 
a constant pressure. Neither of these two varieties of governors 
will act until a change in the rate of revolution of the engine 
occurs, and this change will either admit more or less steam as it 
is faster or slower than that for which the governor is adjusted. 
The commonest form of a governor consists of a vertical shaft to 
which are hinged two arms containing at their lower ends a ball 
of cast iron ; as the shaft revolves the balls are carried outward 
by the action of what is commonly called centrifugal force ; the 
greater the rate of revolution the further will the balls be carried 
outward ; advantage is taken of this property to regulate the ad- 
mission of steam to the engine. The action of the balls and that 
of the valve include two distinct principles and should be consid- 
ered separately ; an excellent valve may be manipulated by an 
indifferent governor and so produce unsatisfactory results ; on the 
other hand, the governor mechanism may be satisfactory in its 
operation, but being connected with a valve not properly balanced, 
is likely to cause a variable rate of revolution in the engine. 

Fly-wheeL — The object in attaching a fly-wheel to an engine 
is to act as a moderator of speed. The action of the steam in the 
cylinder is variable throughout the stroke, against which the rev- 
olution of a heavy wheel acts as a constant resistance and limits 
the variations in speed by absorbing the surplus power of the first 



HANDBOOK ON ENGINEERING. 185 

portion of the stroke, and giving it out during the latter portion. 
The fly-wheel is simply a reservoir of power, it neither creates nor 
destroys it, and the only reason why it is attached to an engine is 
to simply regulate the speed between certain permitted variations 
which are necessary to cause the governor to act, and to equalize 
the rate of revolution for all portions of the stroke, thus convert- 
ing a variable reciprocating power into a constant rotary one. It 
is considered good practice to make the diameter of the fly-wheel 
four times the length of the stroke for ordinary engines, in which 
the stroke is equal to twice the diameter of the cylinder. This 
may be taken as a fair proportion in engine building, and furnishes 
a wheel sufficiently large to equalize the strain and reduce any 
variation in speed to within very narrow limits, if the engine is 
supplied with *a proper governor. The greater the number of 
revolutions at which the engine runs, the smaller in diameter may 
be the fly-wheel, and it may also be largely reduced in weight for 
engines developing the same power. 

Horse-power. — By this term is meant 33,000 pounds raised 
one foot high in one minute. The horse-power of an engine may 
be found by multiplying the area of the piston in square inches 
by the mean effective pressure ; this will give the total 
pressure on the piston ; multiply this total pressure by the 
length of the stroke of the piston in feet ; this will give the 
work done in one stroke of the piston ; multiply this product by 
the number of strokes the piston makes per minute, which will 
give the total work done by the steam in one minute ; to get the 
horse-pow T er, divide this last product by 33,000. From this 
deduct, say, 20 per cent, for various losses, such as friction, con- 
densation, leakage, etc. 

CARE AND MANAGEHENT OF A STEAM ENGINE. 

It is to be supposed to begin with that the engine is correctly 
designed and well made, and that, after a suitable selection of an 



18(5 HANDBOOK ON ENGINEERING. 

engine for the work to be done, nothing now remains except 
proper care and management. 

Lubrication* — The first and all-important thing in regard to 
keeping an engine in good working order is to see that it is 
properly lubricated. This does not imply, neither is it intended 
to encourage, the use of oil to excess ; all that is needed is simply 
a film of oil between the wearing surfaces. It is marvelous how 
small a quantity of oil is required when of good quality and con- 
tinuously applied. There are several self -feeding lubricators in 
the market which have been tested for years and are a pronounced 
success ; these include crank-pin oilers, in which the oscillatory 
motion of the oil makes a very efficient self -feeding device, the 
flow being regulated by means of an adjustable opening to the 
crank-pin, or in the adjustment of a valve by which its lift is reg- 
ulated by each throw of the crank ; and in others by a continual 
flow through a suitable tube containing a wick or other porous 
substance. For stationary engines, it is desirable that the main 
body of the oiler be made of glass that the flow of oil may be 
closely watched and adjusted accordingly. For the reciprocating 
and rotary j>arts of the engine, a modification of the above men- 
tioned oilers may be used. They are of various patterns and 
devices and many of them very good. It is also a good plan to 
have some device by which the cross-head at each end of each 
stroke will take up and carry with it a certain amount of oil ; for 
the lower half of the slide this is not difficult to arrange ; for the 
upper side an automatic feeder placed in the middle of the slides 
will provide ample lubrication. 

For oiling the main bearing there should be two separate 
devices, one an automatic glass oiler ; and in addition, a large 
tallow cup attached to the cap of the bearing. This cup should 
be filled with tallow mixed with powdered plumbago ; the open- 
ings from the bottom of the cup to the shaft should be not less 
than quarter-inch for small engines, and three-eighths to half -inch 



HANDBOOK ON ENGINEERING. 187 

for larger ones ; so long as the main bearing runs cool the tallow 
will remain in the cup unmelted; but if heating begins, the tallow 
will melt and run down on the surface of the revolving shaft, and 
thus provide an efficient remedy when needed. For oiling the 
valves and piston, a self -feeding lubricator should be attached to 
the steam pipe ; this by a continuous flow of oil will be found not 
only satisfactory in its practical working, but economical in the 
use of oil. 

In selecting an oil for an engine, it is in general better to use a 
mineral rather than an animal oil, especially for use in the valve 
chest and cylinder. The objection to an animal oil, and espe- 
cially to tallow or suet, is that it decomposes by the action of heat, 
often coating the surface of the steam chest, the piston ends and 
the cylinder heads with a deposit of hard fatty matter ; or forms 
into small balls not unlike shoemaker's wax. There is no such 
decomposition and formation in connection with mineral oils, 
which may now be had of uniform quality and consistency, and 
at much lower prices than animal oils. 

The slide valve should be kept properly set and should be 
examined occasionally to see that the face and seat are in good 
condition. So long as this is the .case, the valve mechanism and 
the valve itself must be let alone and not tampered with. 

The piston packing will need looking after occasionally to 
see that it does not gum up and stick fast, which it is very likely 
to do when the cylinder is lubricated with tallow or animal oil. 

The rings should fit the cylinder snugly and should be under 
as little tension as possible and insure perfect contact. If the 
rings are set out too tight they are liable to scratch or cut the 
cylinder ; if too loose, the steam will blow through from one end 
of the cylinder, past the piston and into the other. In adjusting 
the springs in the piston, care must be exercised that the adjust- 
ments are such as will keep the piston rod exactly central, to 
prevent springing the rod, or causing excessive wear on the stuf- 



188 HAND BOOK ON ENGINEERING. 

fing box. There are several packings which do not require this 
adjustment, the rings being narrow, and either expanding by 
their own tension or by means of springs underneath. The only 
thing to be done with such a packing is to keep it clean, and 
when lubricated with a mineral oil this is not a difficult matter. 
If it groans, take rings out and file sharp edges off. 

The stuffing boxes whether for the piston or valve-stem need 
,to be looked after carefully, and to prevent leaking, will require 
tightening from time to time. There are several kinds of ready- 
made packings in the market, containing rubber, canvas, garlock, 
soapstone, asbestos and other substances which form the basis of 
a good durable packing. These can be had in sizes suitable for 
all ordinary purposes, and their use is recommended. In the 
absence of any of these, a packing made of clean manila or hemp 
fiber will serve a useful purpose. Formerly it was the only sub- 
stance used, but is being gradually superseded by the other kinds 
mentioned above. In packing the small and delicate parts, such 
as a governor stem, a good packing is made by pleating together 
three or more strands of cotton candle-wick. This is soft, pliable, 
free from anything like grit, and will not get hard until soaked 
with grease and baked into a brittle fiberless substance not easily 
described. 

Crank-pins. — There are few things more troublesome to an 
engineer than a hot crank-pin, and it is sometimes very difficult 
to get at the real reason why it heats. Among the principal rea- 
sons for heating are: the main shaft is not " square " with the 
engine, or, that the pin is not properly fitted to the crank ; or, 
perhaps, it is too small in diameter — defects which are to be 
remedied as soon as practicable. Heating is often caused by the 
boxes being keyed too tightly, or by insufficient lubrication. 
There are now several good self -feeding lubricators in the market 
which will supply the oil to a crank-pin continuously ; these are 
recommended rather than the old style of oil cup, which was 



HANDBOOK ON ENGINEERING. 189 

not only uncertain, but doubtful in its action. Many trouble- 
some crank-pins have been cured of heating by this simple matter 
of constant lubrication. When the crank-pin is rather small for 
the engine and the load variable, there is a possibility of having 
a hot pin at any time ; it is advisable to have ready some 
simple and effective expedient to be applied when it does occur ; 
for this there is perhaps nothing better and safer than a mixture 
of good lard oil and sulphur. 

Connecting: rod brasses* — In quick running engines the 
brasses should be litted metal to metal ; or, if this is not desir- 
able, several strips of tin or sheet brass should be inserted be- 
tween them and keyed up tight. This gives a rigidity to a 
joint which is difficult to secure when the brasses have a certain 
amount of play in the strap. It is a common practice to bore the 
brasses slightly larger than the pin, so that when fitted to it the 
hole shall be slightly oval, and thus permit a freer lubrica- 
tion than is secured by a close fit around the whole circum- 
ference. 

Knocking* — There are several causes which, combined or 
singly, tend to produce knocking in steam engines. In most 
cases the difficulty will be found to be in the connecting rod 
brasses ; but whether in the crank-pin end or at the cross-head is 
not easily determined in all cases. A very slight motion will 
often produce a very disa*greeable noise ; the remedy is, in most 
cases, very simple, and consists in simply tightening the brasses 
by means of the key or other device that may have been pro- 
vided for their adjustment. In adjusting a key it is the common 
practice to drive it down as far as it will go, marking with a 
knife blade the upper edge of the strap, then drive the key back 
until it is loose ; after which drive it down again, until the 
line scratched on the key is within J or J- inch of the top of the 
strap. The size of the strap joint and the judgment of the per- 
son in charge must decide the best distance. This may be done 



190 HANDBOOK ON ENGINEERING. 

at both ends of the connecting rod. On starting the engine, the 
cross-head and crank-pin must be carefully watched, and upon 
the slightest indication of heating, the engine should be stopped 
and the key driven back a little further. A slight warmth is not 
particularly objectionable, and will, as a general thing, correct 
itself after a short run. Knocking is sometimes occasioned by a 
misfit, either in the piston, or cross-head and the piston rod. 
These connections should be carefully examined, and under no 
circumstances should lost motion be permitted at either end of 
the piston rod. 

If the means of securing are such that the person in charge can 
properly fasten the piston to the rod, he should see that it is kept 
tight ; if not, then it should be sent to the repair shop at once, as 
there is no telling when an accident is likely to overtake an engine 
with a loose piston. 

The connection between the piston-rod and cross -head is usu- 
ally fitted with a key and furnishes a ready means of tightening 
the joint, if proper allowance has been made for the draft of the 
key. In case there has not, the piston-rod and cross-head should 
be filed out so that the draft of the key will insure a good tight 
joint when driven clown. 

The main bearing" should be examined and if there should be 
too much lateral movement of the shaft, the side boxes might 
then be adjusted until the shaft turns freely, but has no motion 
other than a rotary one. The cap to the main bearing should also 
be carefully examined, as it may need screwing down and thus 
prevent an upward movement of the shaft at each stroke ; this 
applies more particularly to quick running engines. 

Engines which have been in use for some time are likely to have 
a knock caused by the piston striking the head. This is brought 
about by having a very small clearance in the cylinder and in not 
providing, by suitable liners, for the wear of the connecting rod 
brasses. In a case of this kind, liners should be inserted behind 



HANDBOOK ON ENGINEERING. 191 

the brasses in the connecting rod, or new brasses put in, which 
will restore the piston to its original position. 

Knocking may be caused by defects in the construction of the 
engine ; such, for example, as not being in line, the crank-pin not 
at right angles to the crank, the shaft may be out of line, etc. 

Whenever the cause is one in which it can be shown that it is 
a constructive defect, there is but one remedy, and that is the re- 
placing of that part, or the assembling of the whole until 
perfect truth is had in alignment of all the parts. This will 
require the services of an experienced engineer but all improperly 
fitting pieces should be replaced by new ones as a safeguard 
against accident, which is likely sooner or later to overtake badly 
fitting pieces. 

If the boiler is furnishing wet steam, or priming, so as to force 
water into the steam pipe, it will collect in the cylinder and will 
not only cause knocking, but on account of its being practically 
incompressible there is danger of knocking out a cylinder head, 
bending the piston-rod, or doing other damage to the engine. 
The cylinder cocks should be opened to drain any collected water 
away from the cylinder. 

Repairs* — Whenever it is necessary to make repairs the work 
should be done at once ; oftentimes a single day's delay will in- 
crease the extent and cost fourfold. If an engine is properly 
designed and built, the repairs required ought to be very trivial 
for the first few years it is run, if it has had proper care. It may 
be said in reply to this " true, but accidents will happen in spite 
of every care and precaution." That accidents do occur is true 
enough ; that they occur in spite of every care and precaution is 
not true. In almost every case, accidents may be traced directly 
back to either a want of care, negligence, or to a mistake. 

Fitting" slide-valves* — The practice of fitting a slide-valve to 
its seat by grinding both together with oil and emery, is wrong 
and should never be resorted to. The proper way to fit the sur- 



192 HANDBOOK ON ENGINEERING. 

faces is by scraping ; this insures a more accurate bearing to 
begin with, and will also be entirely free from the fine grains 
of emery which find their way and become imbedded in the 
pores of the casting, and are thus liable to cut the valve face and 
destroy its accuracy. The scraping of the valve and seat has a 
beneficial effect by causing the removal of the fine particles of 
iron, which are loosened by the action of the cutting tool in the 
planing machine, and which ought to be fully removed before the 
engine leaves the manufacturers' hands. Aside from this, it is 
doubtful whether the scraping amounts to anything practically, 
for the reason that the cylinder and valve are fitted cold, and their 
relative positions are distorted by the action of the heat of the 
steam, once the engine is in use. The scraping which simply 
renders the valve face and seat smooth and hard is all that is 
sufficient to begin with, and may be re-scraped after the valve 
has been in use a few days, should it be found necessary, 
which will not often be the case in small and ordinary sized 
engines. 

Eccentric straps are likely to need repairs as soon as any- 
thing about an engine. They should be carefully watched at 
all times. If they are likely to run hot, it is also probable 
there is more or less abrasion or cutting going on, and if 
prompt measures are not taken to arrest it, they are likely to 
cut fast to the eccentric, and a breakage is sure to occur. 

When the straps begin to heat, the bolts should be slackened 
a little, and at night, or perhaps at noon, the straps should be 
taken off and all cuttings carefully removed with a scraper 
(not with a file) ; the rough surfaces on the eccentric should 
be removed in the same manner. 

The straps should be run loose for a few days, gradually 
tightening as a good wearing surface is obtained. 

The main bearing-, if neglected, is a very troublesome journal 
to keep in order. The repairs generally needed are those which 



HANDBOOK ON ENGINEERING. 193 

attend overheating and cutting. The shaft, whenever possible, 
should be lifted out of the bearing, and both the shaft, bottom of 
main bearing and side boxes, carefully scraped and made perfectly 
smooth. It sometimes occurs that small beads of metal project 
above the surface of the shaft which are often so hard that neither 
a scraper nor file will remove them ; chipping is then resorted to 
and the fitting completed with a file and fine emery cloth. 

Heating- of journals* — A very common cause for the heating 
of journals having brasses and boxes composed of two halves, is 
that both halves alter their shape from causes attending their 
wear. Thus, most engineers will have noticed that, although 
there is no wear between the sides of a brass and the jaws of a 
box, yet in time the brass becomes a loose fit in the box. Now, 
since the sides of the brass have, when fitted, no movement in the 
box, it is evident that this cannot have proceeded from wear be- 
tween those surfaces, and it remains to find what causes this 
looseness. Most engineers will also have observed that though 
the bottom or bedding surfaces of a brass and of the box may 
have been carefully filed to fit each other when new, yet if in the 
course of time the brasses be taken out and examined, and more 
especially the bottom brass that receives the weight, the file marks 
will become effaced on all parts where the surfaces have bedded 
together well, the surface having a dull bronze and condensed 
appearance. This is caused by the vibrations under pressure hav- 
ing condensed the metal. Now, this condensation of the metal 
moves or stretches it, and causes the sides of the brass to move 
away from the sides of the box, and, consequently, to close upon 
the journal, creating excessive friction that may often, and very 
often does, cause heating. It is for this reason that on such 
brasses the sides of the brass boxes are, by a majority of engi- 
neers, eased away at and near the joint, and it follows from this 
cause the same easing away is a remedy. 

Governor* — It not infrequently occurs that after an ordinary 
13 



194 HANDBOOK ON ENGINEERING. 

throttling engine has been used a few years, the speed becomes 
variable to such a degree that it interferes with the proper run- 
ning of the machinery. This occurrence can generally be traced 
directly to the governor. When it does occur, the governor 
should be taken apart and thoroughly examined ; if the needed 
repairs are such as can be easily made in an ordinary repair shop, 
they should be made at once ; if not, a new governor should be 
purchased. The price of governors is now so low that it is better 
and more economical to buy a new one than lose the time and 
pay the bills for repairing an old one. 

AUTOMATIC ENGINES. 

In the care and management of this class of engines, it is diffi- 
cult to say just what particular attention they need, owing to the 
variety of styles and the peculiarities of each. As a rule, how- 
ever, they require first, to be kept well oiled ; second, to be kept 
clean ; third, to be kept well packed ; and fourth, to be let alone 
nights and Sundays. There is little doubt that there has been 
more direct loss resulting from a ceaseless tinkering with an 
engine than results from legitimate wear and tear to which the 
engine is subjected. The writer does not wish to be understood 
as saying that builders of this class of engines are infallible ; it 
might be difficult to prove any such assertion in case it was made ; 
but it may be said with truth, that the engines of this class now 
in the market are carefully designed, well proportioned, of good 
materials and workmanship, and as examples of mechanism are 
entitled to take very high rank. The writer knows of several 
engines of this class which have not cost their owners for repairs 
so much as five dollars in five years' constant use. It is essential 
to the economical working of these engines that the cut-off 
mechanism be in good order and properly adjusted. Whenever 
the valves need resetting, the final adjustment should be made 



HANDBOOK ON ENGINEERING. 195 

with a load on the engine and with the indicator attached to the 
cylinder, the valves being set by the card rather than by the eye. 
No general rule can be given for setting the valves, as the prac- 
tice varies with the size and speed of the engine ; nor is any rule 
needed, for the indicator will furnish all the data required. The 
adjustments may then be made so as to secure prompt admission, 
sharp cut-off, prompt release, and the proper compression. 

TO FIND THE DEAD CENTERS. 

When setting the valve of an engine by measuring the lead, as 
is the usual method, it is necessary that the crank be accurately 
placed on the dead centers at each end of the stroke. Sometimes 
an engineer, when adjusting the valves of his engine, will attempt 
to place the crank on the dead center by watching for the point 
at which the travel of the cross-head stops, or by the appearance 
of the connecting-rod as related to the crank. These methods are 
totally unreliable for obtaining accurate results, especially the 
first one mentioned. The travel of the cross-head and the piston 
near the point of reversal of motion is very slow when compared 
with the valve. The velocity of travel of the valve is at nearly 
its maximum amount when the crank is on the dead center, and a 
slight error in finding the dead center point makes a very appre- 
ciable error in the position of the valve, with a subsequent error 
in its proper setting. 

There are several methods for finding the dead center. The 
method that can be recommended and the one that should always 
be used when the dead center of an engine is to be found is that 
familiarly known as " tramming." The dead centers when found 
by this method, are geometrically accurate, no matter if the engine 
is out of level or if the shaft is above or below the axis of the 
cylinder. Some simple tools are required which are generally 
available, with the exception of the trams, which may be readily 



196 



HANDBOOK ON ENGINEERING. 



made for the purpose. Two trams are required, one of which 
should be 6" or 7" long and the other about 24" or 30", as the 
condition may require. The smaller tram may be made of |" 
steel wire with the points turned over at right angles to the body, 
so as to project about 1". The points should be sharpened so 
that a hair line may be drawn by them. The larger tram should 
be made from rod of at least f " diameter and the points made in 
the same way as for the smaller tram. Oftentimes, the long tram 




Finding the Dead Center. 

is made with one leg longer than the other, on account of being 
handier to reach some stationary part, but this is a minor point, 
which has nothing to do with the principle to be described. The 
other tools required are a light hammer, a prick-punch, a pair of 
10" or 12" wing dividers and a hermaphrodite caliper, or a scrib- 
ing block. A piece of chalk will also be found convenient to 
facilitate scribing lines on the metal parts with the trams or 

dividers . 

Having the necessary tools, we are ready to begin operations,— 
you may start at either end of the stroke, as circumstances may 
favor. The fly-wheel is turned so that the crank stands at 
about the angle shown in the accompanying illustration, which 



HANDBOOK ON ENGINEERING. 197 

may, however, be approximated as the operator may desire. The 
effort made, being to give sweep enough to the cross-head to 
allow accurate measurements and still not have such an excessive 
arc on the fly-wheel as to make its bisection difficult. 

A prick mark is made on the guides, or some convenient sta- 
tionary point, as at B, and an arc struck on the cross-head with 
the small tram. At the same time, an arc is scribed on the rim 
of the fly-wheel at G, using some convenient point for the lower 
point of the tram as at K. The fly-wheel is now turned until 
the crank passes the center and the cross-head travels back until 
the scribed line will coincide exactly with the point of the tram 
when held in the same position as in the first case. When this 
point has been reached, the wheel is stopped and a second arc is 
scribed on the fly-wheel rim at F with the tram J. The herma- 
phrodite caliper, or the scribing block, is now used to scribe a 
concentric line D E on the fly-wheel rim and the arc C F is 
bisected with the dividers. When the center H has been accur- 
ately located, it should be carefully prick-marked. The scribing 
of the concentric line D E is a refinement that is not strictly 
necessary if care be taken to locate the points of the dividers at 
the same distance from the outer periphery of the wheel in each 
instance when finding the center H. The marks left by the lathe 
tool will sometimes be plain enough for a guide. When the center 
if has been found, the fly-wheel is turned so that the point of the 
tram will fall into the prick-mark H when its lower end is in the 
stationary point K. When this condition is effected, the crank 
is exactly on the dead center and the position of the valve may 
be taken with confidence that its location at the dead center point 
is accurately found. The same procedure is followed to place the 
crank on the dead center at the opposite end of the stroke. 

The cut on page 198 is an elevation of Tandem Compound 
Engine, showing engine erected on brick foundation. It also 
§&ow§ a lin§ through cylinders 5 also a, liiie gvez the shaft, 



HANDBOOK ON ENGINEERING. 



HANDBOOK ON ENGINEERING. 199 

These lines are used in the erection of a new engine, or to line 
up an old one, or with an engine that is out of line. The cut also 
shows how the foundation is made ; also how the anchor bolt 
is fastened. 

The cut on page 200 shows how to pipe a Twin Tandem 
Compound Condensing Engine. The plan shows two receivers, 
heaters, relief valves, gate valves, etc., and is so arranged 
that either side can be run independently of the other. It 
also shows how to line a pair of these engines up by following 
the lines and noting the distance between each line. An engineer 
would have no trouble in lining up a pair of these engines. 

HOW TO LINE AN ENGINE. 

The method followed when lining different types of engines, 
such as vertical, horizontal, portable, etc. : — 

The method followed in lining any piston engine is essentially 
the same in all cases, as far as determining when adjustments are 
needed. The method of making the adjustments after the char- 
acter and amount of them is determined, depends entirely on the 
construction of the engine, and will necessarily have to be deter- 
mined in each individual case. Lining an engine consists of ad- 
justing the guides so they shall be parallel to the bore of the 
cylinder, and in such a position that the center of the piston 
socket of the cross-head shall coincide with the axis of the cylin- 
der. Under these conditions only, can the piston and cross-head 
travel through the stroke freely, and without distorting any of the 
parts. After this adjustment has been made, the truth of the 
right-angle position of the shaft must be determined as being 
"out of square; " this will make an engine run badly, and is 
often the unsuspected cause of much trouble to engineers. We 
will assume that we have an engine with four-bar or locomotive 
guides, and that the connecting rod, cross-head, back cylinder 



200 



HANDBOOK ON ENGINEERING. 




HANDBOOK ON ENGINEERING 



201 



head and piston have been removed. If the engine is of the 
horizontal type, the first step will properly be to ascertain if the 
engine is level on the foundation, and if not, proceed to make it 
so. After having leveled the engine, stretch a smooth linen 
line, as shown in Fig. 1, through the bore of the cylinder and 
the stuffing box, to a point beyond the shaft, where it should be 
attached to an iron rod driven into the floor. The other end is 
fastened to a cross-bar bolted across the face of the cylinder to 




two of the studs, as shown in Fig.. 4, or the bar may preferably 
be somewhat longer than one-half of the diameter of the cylinder, 
and with a saw cut for a short distance lengthwise at the inner 
end. In this case, it is held by only one of the cylinder studs 
and can be somewhat more easily adjusted. The line or cord is 
adjusted to approximately the proper position, and is drawn taut 
and fastened through the cross-bar by being tied to a short stick 
that is too long to pass through the hole. In this position it is 
held by the friction ; and can be readily adjusted to the required 
position. An assistant is required to move the line in the direc- 
tions indicated, as the work proceeds, and then you are ready to 
center it in the cylinder. The only tool required for this purpose 
is a light pine stick of slightly less length than the radius of the 



202 HANDBOOK ON ENGINEERING. 

bore, and it should have an ordinary pin pushed into the head for 
a " feeler." Now adjust the line in the cylinder so that the head 
of the pin will just tick the line from four points of the counter- 
bore, which is always the part of the cylinder to work from, as it 
is not affected by the wear. The line should then be adjusted 
to the center of the other end of the cylinder, but not from the 
stuffing box, as this is likely to be out of center somewhat. 
Make the adjustment at this end from the counterbore, if pos- 
sible, the same as in the first instance, and then it will be neces- 
sary to try the position of the line in the back end of the cylinder, 
as the changes made at the other end will affect it slightly. After 
the line is truly centered, you are ready to adjust the guides. 
With some types of cross-heads, it is possible to use the cross- 
head for determining the proper location of the guides, but with 
the ordinary form, such as shown in Fig. 2, this cannot be done, 
but you will need a tool similar to that shown in Fig. 3, which 
consists simply of a piece of flat iron long enough to reach across 
the guides, and having a hole drilled and tapped in the center for 
the thumb-screw. This thumb-screw is adjusted so that its point 
is the same distance from the lower side of the bar, as the lower 
face of the wings of the cross-head are from the center of the 
piston socket. To find this distance, lay a straight edge across 
the end of the cross-head and draw the line A B, and then, hav- 
ing found the center of the hole, the measurement may be accur- 
ately taken. The lower guides are now adjusted by the tool, so 
that the point of the screw will tick the line throughout the 
length, and then the top guides are put in position with the cross- 
head in place and adjusted for a proper working fit. 

Before removing the line from the cylinder, however, the shaft 
should be tested for the truth of its right-angle position, which 
may be done by calipering between the crank disc and the line at 
the points H and /. If the distances are equal, the shaft is 
square with the bore of the cylinder, providing, of course, that 



HANDBOOK ON ENGINEERING. 203 

the disc is faced true with the sbaft. If there is any doubt as to 
its accuracy, turn the shaft as nearly half way around as the 
crank-pin will admit without disturbing the line. Then caliper 
the distance of a point on the disc that will not be far removed 
from the first position, thus reducing the chance for error. If 
the shaft shows " out," move the outward bearing until the meas- 
urements show equal in both positions. The horizontal truth of 
the shaft can be found by laying a level on it, and if "out," 
raise or lower the out-board bearing until the level shows fair. 
Work of this kind requires skill and patience and belongs prop- 
erly to the sphere of the chief engineer. It requires a delicacy of 
touch and an appreciation of what is meant by close measurement 
that can come only through experience. In centering the line, 
one should be able to detect when it is as little as T ^^- of an inch 
out of center. A piece of ordinary tissue paper is about .00125 
inch thick. A man should be able, therefore, to adjust a line so 
accurately that if the " feeler," with one or more pieces of the 
paper under it, just clips the line, it will miss the line when one 
thickness is removed. While it may not always be necessary to 
work as closely as this, a person cannot expect to line up engines 
successfully until he has a full knowledge of what this degree of 
accuracy means. 



204 



HANDBOOK ON ENGINEERING. 




HANDBOOK ON ENGINEERING. 205 



CHAPTER XIa. 

DIRECTIONS FOR SETTING UP, ADJUSTING AND RUNNING 
THE IMPROVED CORLISS STEAM ENGINE. 

Location of foundation* — The foundation must beat right 
angles with main line shaft. If main line shaft is not already in 
position, then foundation must be set by two points, located and 
connected' with a line parallel with the buildings, and at right 
angles to an imaginary line through center of cylinder. 

Foundation plans should show all center lines. If a templet 
is furnished to locate the foundation accurately for the mason, the 
center line of engine cylinder and guides and right angle for 
crank center are drawn thereon. 

Cap Stones* — Examine carefully the lap faces of cap stones 
and, if necessary, have them trimmed off by cutter or mason, so 
that each is true and level, and in exactly the plane shown in 
formation plan. 

Cylinders and frame* — Put engine cylinder and frame in 
position and bolt them together. 

Lining off crank shaft and out-end bearing* — Stretch a 
line at right angles to main center line, through main bearing to 
represent center line of crank shaft. See that this line is exactly 
in the center and level. By this line place out-end bearing square 
and true. Put crank shaft in its bearings after bottom box has 
been placed in main bearings. Insert quarter boxes and 
adjusting wedges into main bearing and put cap on. 

To ascertain that shaft is at exact right angles to main center 
line, turn engine shaft until the crank pin comes nearly to the main 



206 HANDBOOK ON ENGINEERING. 

center line, then with a pair of calipers, or rule, measure from 
shoulder of crank-pin to line, and after noting this distance, turn 
the crank back towards opposite center until pin is in same 
relative position to line, and measure again. If both measurements 
do not correspond, out-end bearing must be moved either way as 
required, until measurements show equal. Then take up slack 
around shaft in main bearing, being careful not to force the 
adjusting wedge too tight. 

Fly-wheels* — The fly-wheel is next placed on shaft and firmly 
keyed in position. 

Placing" valve gear* — Steam and exhaust valve covers or bon- 
nets on valve gear side are next bolted to place, taking care that 
no dirt or foreign substance gets between the surface underneath 
the covers. 

Valve stems are inserted from opposite or front of cylinder and 
the valves put in after them, the F head of valve stem entering 
slot in valve. Couple up all valve gear parts, i. e., disc plate, 
valve-stem cranks, valve-connecting rods, dash pots and dash-pot 
rods, valve-rod rocker, eccentric and straps on crank-shaft, first 
and second eccentric rods. The dash pots should be thoroughly 
cleaned and oiled before putting in place. 



ADJUSTMENT OF CORLISS VALVE GEAR WITH SINGLE AND 
DOUBLE ECCENTRICS. 

A brief description of the essential parts of the Corliss engine 
valve gear will assist in obtaining a clear conception of the 
subject. 

When a single eccentric drives both steam and exhaust valves 
the range of cut-off is limited to about half the piston stroke. 
This will become obvious by considering the following necessary 
conditions : — 



HANDBOOK ON ENGINEERING. 



207 



After the eccentric has reached the extreme of its throw as 
shown in Fig. 2 in either direction all valve gear motions are 
reversed . 




Fig. 2. 

The steam valve must be released before the eccentric motion 
is reversed, for if the hook does not strike the knock-off cam 
during its forward motion, it cannot strike it during its return 
motion. 

The maximum exhaust opening, or the middle of the exhaust 
period, must occur when the eccentric is at the extreme of its 
throw as in Fig. 2. 

Now, in order to release the expanded steam in the cylinder 
before the commencement of the return stroke and to secure the 
exhaust closure a little before the end of the return stroke, the 
middle of the exhaust period or the extreme of the eccentric 
throw must evidently occur before the middle of the return 
stroke, and, therefore, the extreme throw of the eccentric in the 
opposite direction must occur before the middle of the forward 
stroke, and the valve must be released before this point is reached 
if released at all. 

It will be understood from the foregoing that late release and 
late exhaust closures are conditions imposed by the single 
eccentric valve gear, and these conditions agree very well with 
moderate rotative speed ; but at higher speed earlier release and 



208 HANDBOOK ON ENGINEERING. 

more compression may be required. This may be effected by 
moving the eccentric forward on the shaft, but the reversing of 
the steam valve motion would then occur at an earlier stage of 
the forward stroke and the range of cut-off would be correspond- 
ingly shortened. Earlier exhaust closure could be had by giving 
the exhaust valve more lap, but this would involve a later release 
of the expanded steam at the end of the stroke. On the other 
hand, shortening the exhaust lap would give earlier release but 
insufficient or no compression. 

In Figs* 3 and 4 similar capital letters of reference indicate 
the same parts of the mechanism. 

Fig. 3 shows all the essential parts of the valve gear. The 
steam valves work in the chambers S S and the exhaust valves 
work in the chambers E E. The double-armed levers D D 
work loosely on the hubs of the. steam bonnets ; they are con- 
nected to the wrist-plate B by the rods K K, the levers M M are 
keyed to the valve stems J J, and are also connected by the rods 
to the dash pots P P. The double-armed levers D carry at 
their outer ends what are called steam hooks, F F, these being pro- 
vided with hardened steel catch plates, which engage with arms 
M M, making the arm M and the hook F work in unison until 
steam is to be cut off. At this point another set of levers or cams 
G G, which are connected by the cam rods H H, to the governor, 
come into play, causing the catch plates on the hooks F to release 
the arms MM, the outer ends of which are then pulled downwards 
by the dash-pot plunger, causing the steam valves to rotate on 
their axis and thus cut off steam. These are the essential fea- 
tures of the Corliss gear. 

The exhaust valve arms N are connected to the wrist-plate by 
the rods L L, and it is seen that all the valves receive their 
motion from the wrist-plate B; the latter receives its motion 
from the hook-rod A; this rod is generally attached to 
a rocker arm not shown ; to this arm the eccentric rod is 



HANDBOOK ON ENGINEERING. 



209 




210 



HANDBOOK ON ENGINEERING. 



also attached. The rocker arm is usually placed about mid- 
way between the wrist-plate and eccentric, and in the center 
of its travel stands in a vertical position. 

The setting" of the valves is not a difficult matter, when, on 
the wrist-plate, its support, valves and cylinder, the customary 
marks have been placed for finding the relative positions of 
wrist-plate and valves. 




vf 



TRAfEU-J „*' 







r& 




Fig. 4. 

Now, referring to Fig. 4, when the back bonnets of the valve 
chambers have been taken off, there will generally be found a mark 
or line, r, on the end of each steam valve s s, coinciding with the 
working or opening edge of each valve ; another line, t, will be 
found on each face of the steam valve chamber coinciding with 
the working edge of the steam port. The exhaust valves and 
their chambers are marked in a similar way, i. e., the line u on 
the end of each exhaust valve coincides with the working edge of 
the valve, and the line x, on the face of ^ach exhaust valve 



HANDBOOK ON ENGINEERING. 211 

chamber, coincides with the working edge of the exhaust port. 
On the hub of the wrist plate will be found three lines n, c, n, 
placed in such a way that when the line c coincides with the 
line b on wrist plate, the wrist plate will stand exactly in the 
center of its motion, and when the line b coincides with either 
of the lines n, n, the wrist plate will be at one of the extreme 
ends v or w of its travel. 

In setting the valves, the first step will be to set the wrist- 
plate in its central position, so that the lines b and c will coin- 
cide, and fasten the wrist-plate in this position by placing a 
piece of paper between it and the washer R on its supporting 
pin. Now set the steam valves so that they will have a slight 
amount of lap, that is to say, the lines r, r, must have moved a 
little beyond the lines t, t. The amount of this lap depends 
much on individual preference and experience ; it ranges from 
T L to J for small engines, and from J to | inch for compara- 
tively large engines. This lap is obtained by lengthening or 
shortening the rods K Khy means of the adjusting nuts. 

Now place the exhaust valves e, e, by lengthening or shorten- 
ing the rods L L by means of the adjusting nuts, in a position 
so that the working edges will just open the exhaust ports, or, 
in other words, place the lines u and x in line with each other 
as indicated in illustration. 

The next step will be to adjust the rocker arm. Set this arm 
in a vertical position by means of a plumb line, and connect the 
eccentric rod to it ; then turn the eccentric around on the shaft, 
and see that the extreme points of travel are at equal distances 
from the plumb line. To secure this a little adjustment in the 
stub end of the eccentric rod may be necessary. Now connect the 
hook rod A to the wrist-plate. The paper between the wrist- 
plate and the washer on the supporting pin should now be taken 
out, so that the wrist-plate which is connected to the valves can 
be swung on its pin. Now turn the eccentric around on the shaft 



212 HANDBOOK. ON ENGINEERING. 

in order to determine the extreme points of travel of the wrist- 
plate. If all parts have been correctly adjusted, the line b will 
coincide with the lines «, .n, at the extreme points of travel ; if 
this is not the case, the hook rod will have to be adjusted at its 
stub end so as to obtain the desired equalized motion of the 
wrist-plate. 

The next step will be to set the valves correctly with reference 
to the position of the crank ; to do this the length of the rods K, 
K, L, and L must not be changed, but the following mode of 
procedure should be followed : Place the crank on one of its dead 
centers (see page 195) and turn the eccentric loosely on the shaft 
in the direction in which the engine is to run, until the steam 
valve nearest to the piston shows an opening or lead of J^ to T x ¥ 
inch. After the proper lead has been given to this valve, secure 
the eccentric, and turn the shaft with eccentric in the same direc- 
tion in which the engine is to run until the crank is on the oppo- 
site dead center, and notice if the opening or lead at this end of 
the cylinder is the same as on the other steam valve ; if not, 
shorten or lengthen slightly, as may appear necessary, the con- 
nection between the wrist-plate and eccentric. Of course much 
adjustment in the length of these connections is not admissible 
without resetting the valves with reference to the wrist-plate. The 
compression on an engine is a very important factor, upon which 
cool and quiet running depends. With exhaust valves line and 
line about 5 per cent compression is secured, which is equal to 1 J' 
for 36" stroke and 2" for 42" stroke. In case more compression 
is desired, the exhaust valves must be given a little lap. 

To set the exhaust valves for a given compression, say, 2 
inches, first measure off 2 inches from the ends of the cross-head 
travel as shown in Fig. 5 (not from the ends of the guide). 
Then turn the crank in the direction it is to run until the end of 
the crosshead reaches the line on the guide. Adjust the exhaust 
valve corresponding to this end of the stroke so that it just closes 



HANDBOOK ON ENGINEERING. 



213 



the port. Turn the crank over the Center and back on the return 
stroke until the opposite end of the cross-head reaches the line on 
the opposite end (to the first mark) of the guide. Then adjust 
the exhaust valve corresponding to this end of the stroke so that 
it just closes the port. Both exhaust valves will then close the 
ports when the piston reaches a point 2 inches from the working 
end of the guide and the engine will then have exactly 2 inches 




Fig. 5. 

compression. If this is found to be too much or too little, as 
determined by the running qualities of the engine, it may be 
varied either way by adjusting the length of the rods L and L, 
being careful to turn each nut exactly the same amount. 

The only thing which remains now to be done is to adjust the 
cam rods iiT, H, to produce an equal cut-off at each end of the 
cylinder. On the column of most Corliss engine governors will 
be found a stop device, sometimes in the form of a loose pin, 
some form of cam motion or movable collar. This device is for 
the purpose of preventing the governor from reaching its lowest 
position, for when it reaches the latter position the valves should 
not hook on. Should the governor belt break or become ineffect- 



214 HANDBOOK ON ENGINEERING. 

ive, the governor will stop and reach its lowest position on the 
column, thereby bringing the safety cam Y in underneath the 
inner member of the hook F which prevents the latter from 
engaging arm M, and as the valves cannot hook on when it is in 
this position the admission of steam to the cylinder is entirely 
shut off and the engine will come to a standstill. 

It will be apparent that the stop on the governor column should 
be removed or otherwise rendered inoperative as soon as the 
engine has attained full speed, and should again be placed in 
active position when stopping the engine in the usual way. As 
the stop just mentioned determines the lowest position of the 
governor at which the valves should hook up, it should be kept 
in place while the foregoing adjustments are being made. 

Next, unhook the reach rod from the wrist plate and by means 
of the starting bar move the wrist plate over until the lines b and 
n are nearly opposite each other. The head end valve should 
now have opened the port to nearly the limit, which may be 
ascertained by the marks on the ends of the valve. Now, adjust 
the governor rod H so that the projection or cam on the disk G 
operated by the governor will come in contact with the inner 
member of the steam hook F, so that the valve will be tripped or 
released when the marks b and n are exactly in line. As all 
governors do not move an equal amount to produce a given 
change in the point of cut-off, it will be safer to hook the reach 
rod on the wrist-plate and have the engine turned in the direction 
in which it is to run, until the head end valve is released, than to 
adjust the cut-off with the use of the starting bar only. To 
prove the correctness of the cut-off adjustment, raise the gover- 
nor balls to a position where they probably would be when at 
work and block them there ; then, with the connections made 
between the eccentric and the wrist-plate, turn the engine shaft 
slowly in the direction in which it is to run, and when the 
valve is released, measure upon the slide the distance which 



HANDBOOK ON ENGINEERING. 



215 



the crosshead has moved from its extreme position. Continue to 
turn the shaft in the same direction, and, when the other valve is 
released, measure the distance through which the crosshead has 
moved from its extreme position, and if the cut-off is equalized, 
these two distances will be equal to each other. If they are not, 
adjust the length of the cam rods until the points of cut-off are 
equal distances from the beginning of the stroke. Replace the 
back bonnets and see that all connections have been properly 
made, which will complete the setting of the valves. 




Fig. 6. 



ADJUSTMENT WITH TWO ECCENTRICS. 

In order to obtain a greater range of cut-off in Corliss engines 
a separate steam and exhaust eccentric is used. With two eccen- 
trics the admission and exhaust valves can be adjusted independ- 
ently, and steam may be cut off anywhere, nearly to the end of 
the stroke. 

The work of setting the valves of a Corliss engine having two 



216 



HANDBOOK ON ENGINEERING. 




HANDBOOK ON ENGINEERING. 217 

eccentrics is not particularly complicated as many engineers seem 
to think. After inspecting the type of releasing gear employed 
and knowing in which direction the engine is to run, finding the 
direction in which to turn the eccentric becomes a very simple 
matter. When setting the steam valves we have one eccentric to 
turn as in the case of the single eccentric engine, and when set- 
ting the exhaust valves another eccentric must be turned, but this 
does not add complication to the work, although it requires a 
little more time. The work of centralizing the positions of the 
various parts, equalizing the movements and setting and adjust- 
ing the valve gear is practically the same as with the single eccen- 
tric engine. Set the wrist-plate central as shown in Fig. 6, and 
adjust the valve rods ; but in this case the steam valves are set 
with negative, lap which is usually a little less than half the 
port opening. The first step is to set the exhaust eccentric 
(as it is generally placed next to the bearing). To do this 
turn the engine until the piston is in the position shown 
in Fig. 7, so as to obtain a compression of about 5 
per cent of the stroke. Then turn the exhaust eccentric 
loosely on the shaft in the direction the engine is to run, until the 
exhaust valves are line and line. Then secure the eccentric and 
turn the engine on the other end in the same position to prove 
the correctness of the other exhaust valve. 

The next step is to set the steam eccentric ; place the crank 
on either one of its dead centers, then turn the steam eccentric 
loosely on the shaft until the steam valve on the same end the 
piston is, has the required opening or lead, which varies from ^" 

to T y\ 

These directions apply to engines in which the reach rod from 
the eccentric is connected to the wrist-plate above the center 
pin R, Fig. No. 3. When the reach rod is connected to wrist- 
plate below the pin R, the eccentric should be turned the opposite 
direction to that in which the engine is to run. 



218 



HANDBOOK ON ENGINEERING. 




HANDBOOK ON ENGINEERING. 



219 



The arrangement of the steam rods in Fig. 3 is in every re- 
spect satisfactory in connection with a single eccentric valve gear, 
for in that case a slow initial valve motion is imperative, and it is 
obtained by the lateral movement of the radius rod. But with 
two eccentrics quicker initial motion is feasible and desirable, and 
it is obtained by reversing the valve motion as in Fig. 6. Sepa- 
rate eccentrics require separate wrist-plates, which are usually 
placed on the same pin. 




/^^X^/f^g- 



Fig. 9. 



Figs* 8 and 9 show how the eccentrics may be placed on the 
shaft. The steam eccentric is at point 4, Fig. "8, the exhaust 
eccentric is at point 1, Fig. 9, and the crank is at its dead center 
at 0. Individual eccentric circles are shown for the sake of clear- 
ness. An imaginaiy motion of the eccentric will point out the 
various events. Referring to Fig. 8, near point 2, at the end of 



220 



HANDBOOK ON ENGINEERING. 



the throw, the hook connects with the steam valve ; at point 3 
the steam edges are at the point of separating and the eccen- 
tric motion 2-3 determines the initial valve motion. When the 
eccentric is at point 4 the crank is at its dead center as 
shown. At point 5 the steam wrist-plate is in its central position 
and in that position the valve does not cover the port, as with 
the single eccentric gear, but the port is open to a certain extent, 
determined by the eccentric motion 3-5. Point 7 marks the end 




of the throw, and the corresponding position of the crank is at O 1 
at about three-quarters of the piston stroke, and the limit of cut- 
off is a little later. If the hook does not strike the knock- 
off cam the valve will remain open until closed by the return 
stroke of the eccentric at point 9, near the middle of the 
return piston stroke. The exhaust action is discernible. Fig, 8, 



HANDBOOK ON ENGINEERING. 



221 



It is similar to the single eccentric action, but with this differ- 
ence, that the release at point 5 occurs at about 95 per cent of 
the stroke, and the exhaust is also cut off at about 95 per cent 
of the return stroke at point 8. 

The motion of the exhaust valve after it has closed the port is 
determined by the eccentric motion 8-2-5, and full period of 
exhaust opening is obtained by the eccentric motion 5-7-8. In 
case the exhaust valve motion is designed and set with lap, Fig. 
10 shows the effect lap has on the exhaust valves. The lap when 
wrist-plate is central is determined by motion A-B. It will be 




Fig. 11. 

noticed that the compression begins at A at about 90 per cent of 
the stroke, and the release at E occurs at 98 per cent of the 
return stroke and the exhaust opening E, 0, A, is shortened. 
Where lap is used on the exhaust valve it has the effect of making 
earlier compression and later release. A valve gear designed to 
be operated by a single eccentric cannot very well be made to cut 
off much later than at half stroke, even when a separate exhaust 
eccentric is added. For the slow initial valve motion requires at 
least half the throw of the eccentric, and the other half is not 
sufficient for a late cut-off, and it will readily be seen from an 
inspection of Figs, 4 and 6, that a quicker initial valve motion in 



222 HANDBOOK ON ENGINEERING. 

Fig. 4 would involve radical changes in the valve gear. However, 
the range of cut-off may be extended by moving the eccentric 
back, sacrificing the lead, and to this there is no objections when 
it does not involve later release. The advantage gained by a 
second eccentric would consist in more compression and earlier 
release. After setting the valves and making the final adjustment, 
if it is convenient an indicator should be applied to the engine 
when at work to verify the adjustment of the valves for the best 
possible conditions for economical operation. 

Fig. 10 indicates position of eccentric at f cut off which can 
be extended some by giving the steam valves a little more nega- 
tive lap, but as this shortens the amount of lap when closed, it 
may cause leakage in the steam valves. 

COMPOUND ENGINE. 

The compound engine is practically two single engines con- 
nected together and so arranged that the exhaust steam from 
one engine passes into and becomes the " live " steam for the 
other, in other words the first, or high pressure cylinder receives 
its supply of steam from the boiler and the second or low 
pressure cylinder receives its supply from the high pressure 
cylinder. The object of the compound engine is to enable the 
steam to expand to the lowest possible pressure with the least 
loss by condensation. When steam expands its temperature 
decreases, so that by the time the piston reaches the end of the 
stroke the temperature of the steam and consequently the tem- 
perature of the cylinder walls is considerably below the temper- 
ature of the incoming steam. The fresh steam of hight empera- 
ture coming from the boiler comes in contact with the walls of 
the cylinder which have been cooled to the temperature of the 
exhaust steam, and the result is a considerable portion of the 
fresh steam is condensed, the latent heat serving to reheat the 



HANDBOOK ON ENGINEERING. 



223 



3 

crq" 





■& 



224 HANDBOOK ON ENGINEERING. 

cylinder walls. It will be understood that were it possible to 
keep the cylinder at a higher temperature, less steam would be 
condensed in warming it at each stroke and consequently more 
steam would be available for useful work. In the compound 
engine the steam is expanded partly in one cylinder and partly 
in the other so that the difference between the temperatures of the 
incoming and exhaust steam in each cylinder is greatly reduced. 
By this means steam may be expanded from a given initial pres- 
sure to a given final pressure with a loss of nearly twenty-five 
per cent less than would be incurred were the same expansion to 
take place in a single cylinder. It is due principally to avoiding 
the loss by cylinder condensation that the compound engine, 
considered as a type of engine, can perform nearly twenty -five 
per cent more work with the same weight of steam than can be 
obtained when the steam is expanded in one cylinder only. 

In order to utilize the low pressure steam escaping from the 
high pressure cylinder it is necessary to provide a larger area 
of piston so that the low pressure steam acting on a large sur- 
face will do as much work as the high pressure steam acting on a 
smaller area. It is for this reason that the low pressure cylinder 
of compound engines is always made larger than the high pressure 
cylinder. The required size of low pressure cylinder for a given 
size of high pressure, depends upon the number of times the 
steam is to be expanded, the initial steam pressure and the nature 
of the work the engine is intended for. For steady loads the 
difference in the size of the two cylinders may be greater than 
where the load is constantly changing between wide limits as 
nearly always occurs in street railway service. 

Compound engines, as this term is generally employed, are 
built of two types, the tandem compound, Fig. 1, and the cross 
compound, Fig. 2. In the tandem compound the work of both 
pistons is transmitted to the crank through one piston rod, cross- 
head and connecting rod, while in the cross compound there are 



HANDBOOK ON ENGINEERING. 



225 




226 HANDBOOK ON ENGINEERING. 

two complete engines placed side by side, the cranks of which 
are generally set 90 degrees apart. It will be seen that in the 
tandem compound engine it makes but little difference from the 
mechanical standpoint whether the work is divided evenly between 
the two cylinders or not because both pistons move in unison 
and drive the same crank. In the cross compound engine it is 
necessary, in order to secure a uniform turning effort at the 
shaft, to have the work divided as nearly equally between the 
two cylinders as the conditions will permit. In the tandem com- 
pound engine the principal consideration is the proper working 
of the steam, and the sizes of the cylinders are determined by 
the number of expansions to be effected in both cylinders, or 
the total number of expansions, as it is called, and the initial 
pressure. As the equal division of the work between the two 
cylinders in compound engines is essential, the ratio of the cylin- 
ders is generally for noncondensing 21 to 1 for 100 lbs., 2} to 1 
for 125 lbs., and 3 to 1 for 150 lbs. initial pressure, and for con- 
densing 3 to 1 for 100 lbs., 3J to 1 for 125 lbs., and 4 to 1 for 
150 lbs., initial pressure. 

The number of expansions required in a compound engine is 
represented by the quotient of the absolute initial j)ressure divided 
by the absolute terminal pressure. If steam is to be used at 105 
pounds gauge pressure and is to be expanded down to 10 pounds 

105 + 15 
absolute in the low pressure cylinder, there will be r^ = ^ 

expansions. A simple rule for finding the ratio of the area of 
cylinders for noncondensing, is to divide the absolute initial pres- 
sure by the terminal pressure which equals the expansions in both 
cylinders and the square root of total expansions equals the ratio 
of cylinders. 

For example: 150 lbs. initial pressure plus 15 lbs. equals 165 
lbs. absolute initial pressure divided by 16 lbs. terminal pressure 
equals 10.3 total expansions, and the square root of 10.3 equals 



HANDBOOK ON ENGINEERING. 227 

3.2 equals ratio of cylinders. Care should be taken in non- 
condensing engines so that the ratio of the low pressure cylinder 
is not too large, as in such cases the steam in low pressure cylin- 
der would expand to less than the atmospheric pressure, and 
thus make loops on indicator card, which would incur a serious 
loss. 

The calculation of the diameters of cylinders for a compound 
condensing engine when the data are given, follows. Take an 
engine that is to develop 500 horse power with an initial pressure 
of 105 pounds gauge, or 120 pounds absolute, the steam to be 
expanded to a terminal pressure of 6 pounds absolute. The total 
expansion of steam in both cylinders is 120 -~- 6 =20. 

Expansion in each cylinder = ^20 = 4.47. 

Point of cut-off in each cylinder, per cent of stroke = = 

22.3 per cent, 1 -f- hyp* log* of expansion in each cylinder = 1 -f- 

hyp. log. 4.47=2.497. 

Terminal and back pressure in high pressure cylinder, and the 

120 
initial pressure in thelow = jTy = 26.8 pounds. 

Mean effective pressure in h. p. cyl. = 26.8 X 2.497 — 26.8 
= 40.11 pounds. 

Mean effective pressure in 1. p. cyl. (assuming 3 lbs. back" 
press.) = 6 X 2.497 — 3 = 11.98 pounds. 

If half the work is to be done in each cylinder, which is de- 
sirable in cross compound engines, each cylinder must do 250 
horse power of work. Assuming the piston speed to be 600 feet 
per minute, the area of the low pressure cylinder is 

33000 XH.P. 33,000 X 25 

Piston speed X effective press. — 600 X H-98 = 1U7 ' 7 square 
inches =38 ins. diameter. 

a *t t, r a l i • 33,000X250 

Area of high pressure cylinder by same rule is : — I 

& 600X40.11 

= 342.3 square inches = 21 inches diameter. 



228 



HANDBOOK ON ENGINEERING. 



Ratio of cyl. : 



40.11 
11.98 



= 3.3 to one. 



The clearance and the areas of the piston rods have not been 
taken account of by separate processes in the foregoing calcu- 
lations. These should always be included when rnakiug calcu- 
lations involving the pressure and expansion of steam in engine 
cylinders. The method of finding the number of expansions 
taking place in a compound engine may be readily understood 
by referring to the diagram, Fig. 3. The shaded area in the 





r /*&/ 


a i/o/s. 


3 foVs. 


/ Vol £ l/o/s. 3- v*/s. 


ftp 






w 






ww<, 






1 




Ww 















Fig. 3. 

smaller cylinder represents the initial volume of steam in the 
high pressure cylinder, that is to say, this represents the volume 
of steam taken from the boiler for one stroke, or during one-half 
revolution. The point of cut-off is at one-third stroke and the 
area of the low pressure cylinder is three times that of the high 
pressure cylinder. It will be seen that when the low pressure 
piston moves to one-third stroke the volume of the cylinder V 
behind the piston is equal to the volume of the entire high pres- 
sure cylinder. This shows that the capacity or contents of the low 
pressure cylinder is three times that of the high so that for every 



HANDBOOK ON ENGINEERING. 



229 



volume of steam and therefore for every expansion taking place in 
the high pressure cylinder there will be three volumes, and three 
expansions taking place in the low pressure cylinder. This 
shows why the total number of expansions in a compound engine 
is the number in the high pressure cylinder multiplied by the 
number in the low pressure cylinder. In the diagram, Fig. 3, 
when the small piston reaches the end of the stroke the steam 
will have expanded three times, that is, it will occupy three times 
the space it did at the point of cut-off. Now when the large 
piston reaches the end of the stroke each of the three volumes a, 
a and a, Fig. 4, will have been expanded three more times and 
the total will be 3X3 = 9 expansions, that is, the original 
volume a, Fig. 3, will then occupy nine times the space it did when 





£#*/ rf&Sfi/re Cy/- 


/?/?/? /Zvssi/& fy/. 








&' 


a & 


a* 





















Fig. 4. 



first let into the high pressure cylinder. To find the number of 
expansions in a compound engine multiply the number of expan- 
sions in the high pressure cylinder by the number in the low, or 
multiply the number of expansions in the high pressure cylinder 
by the ratio of cylinder areas ; the product will be the number 
required. 

Again referring to Fig. 4, it will be seen that the low pressure 
cylinder must receive a high-pressure cylinderful of steam at each 



230 HANDBOOK ON ENGINEERING. 

stroke otherwise the pressure in the receiver and the back pressure 
on the high pressure piston will rise too high and a loss of power 
will result, or if the pressure be too low in the larger cylinder the 
small piston will drive the larger one which will again result in 
loss of power. It has been shown that the volume of both 
cylinders vary in proportion to the areas, that is, if the areas are 
as 1 to 3 then when both pistons have reached, say, one-third 
stroke the volume of one will be 3 times the volume of the other, 
and when the larger piston in this case travels one-third of the 
stroke the capacity of the low pressure cylinder behind the piston 
will then be equal to the whole of the smaller cylinder and will be 
capable of containing all the steam used during a full stroke of 
the smaller piston, or a high-pressure cylinderful of steam. This 
steam then expands during the remaining two-thirds of the stroke. 
Now it will be readily understood that if a cut-off valve were pro- 

Hish Pressure Diasram. 



Lav/ Pressure Dkeram. 



Vacuum Line 

Fig. 6. 

vided on the low pressure cylinder and is set to cut off at less than 
one-third stroke (with a ratio of cylinder areas 1 to 3) the low 
pressure cylinder will not take a high pressure cylinderful of 
steam when steam is cut off, and the pressure in the receiver must 
necessarily rise. Reducing the volume of steam entering the low 
pressure cylinder apparently tends to lessen the work done by the 
larger piston and consequently more work must apparently be 



HANDBOOK ON ENGINEERING. 231 

done by the high pressure piston. This in turn causes a later 
cut-off in the small cylinder as shown in Fig. 5, dotted lines, 
which serves to neutralize the effect of the higher back pressure 
so that while the cut-off has been made later, the mean effective 
pressure remains practically the same. The higher back pressure 
on the small piston means a higher initial pressure in the low 
pressure cylinder, see Fig. 6 dotted lines, which causes more 
power to be developed in the latter cylinder. Thus it is seen 
that, within certain limits, shortening the cut-off in the low pres- 
sure cylinder puts more of the load upon the low pressure piston. 

On the other hand when the low pressure piston is doing more 
work than the high pressure, the cut-off in the low pressure 
cylinder may be lengthened. This permits the low pressure 
cylinder taking more steam and consequently the receiver pressure 
and the back pressure on the high pressure piston are reduced 
and the work done by the high pressure piston is thus increased. 
By manipulating the cut-off on the low pressure cylinder the load 
on the two pistons may be equalized or very nearly so except 
when the engine is considerably underloaded or overloaded. The 
range of maximum economy is not as great with the compound as 
with the simple engine, that is to say, the load may be varied 
more widely from the point where the best economy is obtained, 
in the simple engine than in the compound which is due to the 
large difference in cylinder areas in the latter engine. At very 
early cut-off both the high pressure and the low pressure cylinders 
work the steam very similarly to the simple engine and as the loss 
by cylinder condensation increases with an increase in the range 
of temperatures it follows that an underloaded compound engine 
is but little if any more economical than a simple engine working 
with a similar initial point of cut-off. 

In compound automatic cut-off engines the point of cut-off will 
be nominally the same in both cylinders, we say nominally (in 
name only) because the initial pressure and the extent of the 



232 HANDBOOK ON ENGINEERING. 

vacuum have some influence upon the receiver pressure and the 
mean effective pressure in the low pressure cylinder. In most 
compound engines in which the cut-off mechanism of both cylin- 
ders are operated by a single governor, provision is made for 
adjusting the cut-off of the low pressure cylinder relative to that 
in the high, so that while the nominal cut-off may be, say, one- 
fourth stroke, the actual points of cut-off maybe one-fourth in the 
high pressure and T 5 ¥ in the low pressure cylinder, the governor, 
however, varying both points of cut-off as the load changes. 

HORSE POWER OF COMPOUND ENGINE. 

Little can be done in finding the horse power of compound en- 
gines without the indicator because of the uncertainty of the points 
of cut-off and consequently of the back pressure and mean effec- 
tive pressures. The mean effective pressure in each cylinder may 
be computed by using assumed data, by the same rules given 
for simple engines, but it will readily be understood that assumed 
data furnishes assumed results only. Knowing the mean effective 
pressure areas and speed of the pistons the horse power of a 
compound engine is found as follows: Multiply the areas of 
the high pressure piston by its mean effective pressure and 
divide by the area of the low pressure piston, then add this quotient 
to the mean effective pressure in the low pressure cylinder.* 
Call this answer 1. Multiply the area of the low pressure 
piston by the piston speed in feet per minute and by answer 1, 
and divide the last product by 33,000; the quotient will be 
the indicated horse power. 

CONDENSING ENGINES. 
It has been explained that the atmosphere exerts a pressure 
of about 15 lbs. per square inch on all surfaces with which it 

* This quantity is to be taken as the M. E. P. when finding steam con- 
sumption of compound engine. 



HANDBOOK ON ENGINEERING. 233 

is in contact. The atmosphere is in contact with one side of 
an engine piston when the exhaust is open, and, consequently, 

i the steam in pushing the piston forward, has to overcome this 
atmospheric pressure of 15 lbs. per square inch. The useful 
pressure of steam is, therefore, whatever pressure there is 

I above the pressure of the atmosphere, and this is the pressure 

: that the steam gauge shows. When the gauge says 60 lbs. we 
really have 75 lbs., but 15 lbs. of it does not count, because it 
is balanced by the atmospheric pressure on the other side of 

i the piston. If we had sixty -pound steam pressing on the pis- 
ton and could get rid of the atmospheric pressure on the side 
of the piston, the steam' would exert a force of 75 lbs. per square 
inch, a very respectable gain, indeed. We might remove the air 
pressure by pumping it out, but the amount of power required in 
doing the pumping would be equal precisely to all gain hoped for, 
plus the friction of the punip ; therefore, there would be an 
actual loss in the operation. But there is another way of remov- 
ing the air pressure. It has been explained that a cubic inch of 
water vaporizes and expands into a cubic foot of steam at atmos- 
pheric pressure. Jf, after getting this cubic foot of steam, we 
take the heat out of it, we again turn it into the cubic inch of 
water. Assume the engine cylinder to hold just a cubic foot of 
steam, and assume that the stroke is complete and ready for the 
exhaust valve to open and permit this foot of steam to escape, 
and assume that this cubic foot of steam has expanded 
down to atmospheric pressure, that is, 15 lbs., absolute pressure. 
Now, instead of opening the cylinder to the atmosphere, we dose 
the cylinder with cold water. The heat leaves the steam and 
goes into the water and the steam turns to water, leaving in the 
cylinder the condensed steam in the form of a cubic inch of 
water. The steam formerly filled the cylinder, and now it fills 
but a cubic inch of it, consequently, we have produced in the 
cylinder a vacuum which has the effect of adding about 15 lbs. 



234 HANDBOOK ON ENGINEERING. 

per square inch, to the force of the steam on the other side of the 
piston, by virtue of removing that much resistance to its forward 
motion. The heat which was in the steam has gone into the con- 
densing water, except the trifle that remains in the cubic inch of 
condensed water. We must get this condensed water out of the 
cylinder, and it will be an advantage to pump it back into the 
boiler, for it is pure and it is hot. 

This is the general principle of the condensing engine. It 
gives us the grand advantage of a heavy increase in the useful 
pressure acting to push the piston forward ; it gives us pure 
water for use in the boiler, and it saves in the feed-water the 
heat that would otherwise go out of the exhaust pipe. But it is 
not practicable to condense the steam in the cylinder by dosing 
the cylinder with cold water. In practice, the steam is allowed 
to go into a separate condensing vessel, called the condenser! 
The condenser is precisely the opposite of the boiler. The boiler 
is the machine for putting heat into the steam to vaporize it, and 
the condenser is the machine for taking heat out of the steam and 
turning it into water again. In the condensing engine, one of 
these machines is pushing on the piston and the other machine is 
pulling on the piston. The gain by condensing is so great that 
it is a profitable piece of business to apply a condenser to any 
large non-condensing engine. The condenser requires a pump to 
withdraw the water of condensation, and this pump must be in 
reality an air-pump. In practice, they employ an air-pump and 
condenser combined in one structure, separate from the engine, 
and driven either by rod connection from the engine, or by a belli 
from the engine, or by an independent steam pump. The arrange- 
ment will depend much upon the situation. The belt-driven pump 
permits of the condenser being set in any convenient position 
independent of the engine. 



HANDBOOK ON ENGINEERING. 235 



CONDENSERS. 

When steam expands in the cylinder of a steam engine, its 
pressure gradually reduces and ultimately becomes so small that 
it cannot profitably be used for driving the piston. At this stage, 
a time has arrived when the attenuated vapor should be disposed 
of by some method, so as not to exert any back pressure or 
resistance to the return of the piston. If there were no atmos- 
pheric pressure, exhausting into the open air would effect the 
desired object. But, as there is in reality a pressure of about 
14.7 pounds per square inch, due to the weight of the super- 
incumbent atmosphere, it follows that steam in a non-condensing 
engine cannot economically be expanded below this pressure, and 
must eventually be exhausted against the atmosphere, which 
exerts a back pressure to that extent. 

It is evident that if this back pressure be removed, the engine 
will not only be aided by the exhausting side of the piston being 
relieved of a resistance of 14.7 pounds per square inch, but 
moreover, as the exhaust or release of the steam from the engine 
cylinder will be against no pressure, the steam can be expanded 
in the cylinder quite, or nearly, to absolute of pressure, and 
thus its full expansive power can be obtained. 

Contact, in a closed vessel, with a spray of cold water, or with 
one side of a series of tubes, on the other side of which cold 
water is circulating, deprives the steam of nearly all its latent 
heat, and condenses it. In either case the act of condensation is 



236 HANDBOOK ON ENGINEERING. 

almost instantaneous. A change of state occurs and the vapor 
steam is reduced to water. As this water of condensation only 
occupies about one sixteen-hundredths of the space filled by 
the steam from which it is formed, it follows that the remainder 
of the space is void or vacant, and no pressure exists. Now, the 
expanded steam from the engine is conducted into this empty or 
vacuous space, and, as it meets with no resistance, the very limit 
of its usefulness is reached. 

The vessel in which this condensation of steam takes place is 
the condensing chamber. The cold water that produces the con- 
densation is the injection water ; and the heated water, on leaving 
the condenser, is the discharge water. To make the action of the 
condensing apparatus continuous, the flow of the injection water 
and the removal of the discharge water, including the water from 
the liquefaction of the steam, must likewise be continuous. 

The vacuum in the condenser is not quite perfect, because the 
cold injection water is heated by the steam and emits a vapor of 
a tension due to the temperature. When the temperature is 110 
degrees Fahr,, the tension or pressure of the vapor will be 
represented by about 4" of mercury ; that is, when the mercury in 
the ordinary barometer stands at 30", a barometer with the space 
above the mercury communicating with the condenser, will stand 
at about 20". The imperfection of vacuum is not wholly traceable 
to the vapor in' the condenser, but also to the presence of air, a 
small quantity of which enters with the injection water and with 
the steam ; the larger part, however, comes through air leaks and 
faultly connections and badly packed stuffing boxes. The air 
would gradually accumulate until it destroyed the vacuum, if 
provision were not made to constantly withdraw it, together with 
the heated water by means of a pump. 

The amount of water required to thoroughly condense the 
steam from an engine is dependent upon two conditions : the total 
heat and volume of the steam, and the temperature of the injection 



HANDBOOK ON ENGINEERING. 237 

water. The former represents the work to be done, and the latter 
the value of the water by whose cooling agency the work of con- 
densation of the steam is to be accomplished. Generally stated, 
with 26" vacuum, the injection water at ordinary temperature, not 
exceeding 70° Fahr., from 20 to 30 times the quantity of water 
evaporated in the boilers will be required for the complete 
liquefaction of the exhaust steam. The efficiency of the injection 
water decreases very rapidly as its temperature increases, and at 
80° and 90° Fahr. , very much larger quantities are to be employed. 
Under the conditions of common temperature of water and a 
vacuum of 26" of mercury, the injection water necessary per 
H. P. developed by the engine, will be from 1 J 'gallons per minute 
when the steam admission is for one-fourth of the stroke, up to 
two gallons per minute, when the steam is carried three-fourths of 
the stroke of the engine. 



238 



HANDBOOK ON ENGINEERING. 



SETTING THE PISTON TYPE OF VALVE. 

The simple piston valve admitting steam between the pistons 
is, in operation, the reverse of the plain D slide valve, which ad- 
mits steam at the outer edges, or ends of the valve. To make 
this still clearer it may be said that were the live steam to enter 
through the exhaust cavity of the D slide valve its operation and 
the position of the eccentric relative to the crank would be iden- 




/ 




Fig. 2 




tical to that piston valve. Fig. 1 illustrates the similarity of 
action and eccentric positions were these conditions to obtain. 

In these types of valve, as ordinarily employed, the steam is 
admitted at the ends of the slide valve, and between the pistons 
or at the middle of the piston valve. The change from the end 
to the middle of the valve necessitates a change in the position 
of the eccentric relative to the crank in order to have the direc- 
tion of rotation remain the same. The positions of the eccentric 
when driving the simple D valve, and the piston valve, are indi- 



HANDBOOK ON ENGINEERING. 



239 



cated in Fig. 2. It will be noticed that the crank revolves in the 
same direction in both cases, and that when the crank leaves the 
dead center, moving in the direction of the arrow, the same port, 
viz., the one at the head end of the cylinder, will be opened at the 
same time and to the same extent. This proves the positions as 
shown to be correct and illustrates why the eccentric must be 
moved in the same direction the engine is to run with the D valve, 
and in the opposite direction with the piston valve, in order to 
secure the same direction of rotation in the engine. 





Fig. a 

f 



mmmmMmmmz? 1 




When setting valves it is a good plan to obtain as much uni- 
formity of methods as possible, because of the liability to con- 
fusion when methods involving different movements of the 
eccentric are employed. In ail the directions that follow it is 
assumed that the crank is placed on the dead center (sae page 
195) nearest the cylinder so that wiien setting the different styles 
of valves, the same steam port will always be opened first, namely, 
the one at the head end of the cylinder. The engine, it will be 



240 



HANDBOOK ON ENGINEERING. 



seen, is thus treated as though it contained but one steam port, 
which greatly simplifies matters. 

In order to show that each particular form of valve of the same 
type does not require different methods for its proper adjustment, 
both the simple piston valve andjthe main valve of the round riding 
cut-off are illustrated together, the same directions applying to 
both. 

Where marks appear upon the valve stem, or seat, it becomes 
an easy matter to set a valve quickly and correctly but when these 
do not appear a different method must be pursued for obtaining 
them. First remove the chest covers at both ends of the chest 








$Ct*y?/<s P/sfo/7.fa//e. 



Flg.s i_ \ 



/?/<&/ /7 ya/ye - /?/a'/rtg Cc/r &??_ 



Fig. 3 



and also the valve (both styles) from the chest and lay it upon a 
clean place on the floor, or bench. Procure a piece of sheet steel 
about Jg inch thick and file it to the form shown in Fig. 3. 
Make the length of the gauge thus formed equal to the thickness 
of the piston on the valve plus the lead, which may betaken as j% 
inch. Replace the valve in the chest and connect it to the valve 
stem. Turn the eccentric from one extreme position to the other 
and see that the valve opens the ports an equal amount. It is not 
necessary that the ports be opened exactly wide, the object being 
to secure exactly the same opening at each end of the valve. If 
the head end port is opened farther than the other, the eccentric 



HANDBOOK ON ENGINEERING. 



241 



tod should be lengthened an amount equal to one-half the differ- 
ence, and should the port at the crank end be opened farthest, 
tie eccentric rod should be shortened a like amount. 

Turn the eccentric to the extreme position farthest from the 
cylnder. Then place the small end of the gauge against the inner 
edge of the port, and with a scriber make a fine line (a) on the 
seat as shown in Fig. 4. Remove the gauge, and turn the eccen- 
tric 11 the same direction the engine is to run until the end of the 
valve reaches the fine line on the seat. Secure the eccentric to 
the shaft, being careful not to move the eccentric in either direc- 
tion. Now turn the crank in the direction it is to run uDtil the 
eccentric reaches the extreme position nearest the cylinder. The 
gauge is now placed against the edge of the opposite port and a 




Tig. 4. 



fine line drawn on the seat, at the end of the gauge, in the same 
manner as shown in Fig. 4. Turn the crank to the dead center 
farthest from the cylinder when the end of the valve should have 
just reached the line on the seat, If it does not, the crank 
should be turned sufficiently to enable the distance between the 
valve and the mark, being measured. The eccentric rod is then 
to be adjusted so as to move the valve a distance equal to one- 
half of what the valve lacks of exactly reaching the line on the 
seat. The valve will then open both ports to the extent of the 

16 



242 HANDBOOK ON ENGINEERING. 

lead when the crank occupies the exact dead centers. It is very 
desirable to have a method of setting the valve without removing 
the chest covers. By the aid of simple gauges this can be readily 
accomplished. Take a piece of steel wire and sharpen tie 
ends and bend into the form shown in Fig 5. With a priok 
punch make a mark (6) on the guide block, place one end of 
gauge in this mark and make another mark (c) where the opposite 
end of the gauge touches the valve stem. This gauge enables 
the valve stem being disconnected from the valve^tem guide 
block, and the chest cover put on, and the stem afterward con- 
nected up again in exactly the same position (see page ). 
Having made this second gauge, place the crank on the exact 
dead center nearest the cylinder. Then make a prick punch mark 
(d) on the stuffing box, place one end of the gauge in this mark 
and then make a second mark (e) where the other end of the 
gauge touches the valve stem. It will readily be seen that when 
testing the setting of the valve all that is necessary is to place 
the crank on the dead center nearest the cylinder, then place the 
gauge the mark (d) on the stuffing-box, and have the eccentric 
moved until the punch mark (e) on the valve stem falls under 
the point of the gauge. The valve will then have opened 
the port to the extent of the lead, because it was in 
this position when the gauge and the marks were first 
made. If the punch marks are nicely made and not too large 
the extent of the lead opening may be measured at both ports, 
by turning the crank to the opposite dead center and making a 
second punch mark (/) on the valve stem by means of the gauge. 
These two guages should be carefully preserved from injury and 
from being mislaid so that in case of emergency, such as the 
slipping of an eccentric, the latter can be returned to its correct 
position without unnecessary loss of time. 



HANDBOOK ON ENGINEERING. 



243 



SETTING THE CUT=OFF VALVE. 

The following directions are applicable to both the flat slide 
and the round types of cut-off valves. 

The point of latest cut-off is seldom known exactly by the 
average engineer because of its unimportance while the engine is 
in running order, and as this point varies with different engines 
it is advisable to discard it as an element in valve setting. First 
place the main valve in its position of mid-travel, that is, place 
it centrally over the ports. This may be accomplished by finding 
the center between the punch marks (/) and (e) on the valve 
stem, bringing the center mark g under the point of the gauge in 
the manner shown in Fig. 5. The travel of the cut-off valve must 
first be equalized which is accomplished by turning the cut-off 




Fig* 5 



eccentric to its extreme positions and noting the travel of the 
cut-off valve over the ports of the main valve. The cut-off eccen- 
tric rod should be lengthened or shortened so that the cut-off 
valve will travel evenly over the ports in the main valve. This, 
of course, is obtained by measuring the distance from the edge 
of the ports in the main valve to the ends of the cut-off valve when 
the latter occupies its extreme positions. 

First, assume the engine to have a fixed, or a hand-adjusted 
cut-off, and that the cut-off valve is to be set to cut off steam at 



244 



HANDBOOK ON ENGINEERING. 



one-half stroke. Place the crank on the dead center (see page 
195) and the full part of the cut-off eccentric the same. Then 
measure off one-half the length of the stroke from the end of t!ie 
cross-head as in Fig. 6 and make a light line / on the guide. Turn 
the engine in the direction it is to run until the end of cross-head 




^y^/3><w» 



reaches the line / on the guide. The piston will now have com- 
pleted one-half its stroke. Turn the cut-off eccentric in the 
direction the engine is to run until the cut-off valve opens the 
port in the main valve wide and just closes the port again in the 
main valve. 

Secure the cut-off eccentric to the shaft at this point. 
Turn the crank over to the opposite dead center and far enough 
beyond the center so that the same end of the crosshead will have 
again reached the line (/) on the guide as in Fig. 6. The piston 
will now have completed one-half of the return stroke and the 
cut-off valve should have just closed the port in the main valve. 
If the cut-off valve has moved too far, or not far enough, measure 
the amount it lacks of just closing the port and then adjust the 
cut-off eccentric rod an amount equal to one-half the amount of 



HANDBOOK ON ENGINEERING. 245 

the discrepancy. The cut-off valve will then close the port in the 
main valve at exactly the same point in both forward and return 
strokes. 

When an automatic cut-off engine, in which the cut-off 
eccentric is operated by a shaft governor, first block out the 
weights to their extreme position or against the stops, the travel 
of the cut-off valve having been previously equalized in the 
manner explained above. Then turn the crank to the dead center, 
preferably the one nearest the cylinder, and turn the full port of 
the cut-off eccentric to the same position as a starting point. 
Then turn the eccentric in the direction the engine is to run until 
the cut-off valve opens the port in the main valve to the extent of 
the lead or from J- ¥ to J^ inch. Secure the governor wheel to 
the shaft at this point. Turn the crank to the opposite dead 
center and see that the cut-off valve has opened the port in the 
main valve to the same extento If it has not done so, adjust the 
length of the eccentric rod an amount equal to one-half the differ- 
ence between the two lead openings. Take out the blocks and 
the work will be completed. It will readily be understood that, 
were the speed of the engine to reach a point, where the 
governor weights strike the stops, the cut-off valve will admit 
only steam enough to fill the clearance, which should always be 
done, because while it does not tend to accelerate the speed it 
does prevent forming a vacuum in the cylinder, and from drawing 
in whatever may happen to be in the vicinity of the end of the 
exhaust pipe. The point of latest cut-off will then take care of 
itself and will occur at that point for which the valve and gear 
were designed. 

FLAT VALVE RIDING CUT-OFF. 

In medium and slow speed engines it is very desirable to have 
a uniform point of release and constant compression. If the 
engine is of the automatic cut-off variety the point of cut-off will 



246 



HANDBOOK ON ENGINEERING. 



necessarily change with each change of load, and if the steam is 
released, and the point of compression determined by the valve 
effecting the out-off , it is plain that as the cut-off varies, the point 
of exhaust and of compression must also vary proportionately. 
In order to secure a uniform amount of lead, a constant point of 
release and of compression, it is necessary that the valve deter- 
mining these points be given a constant travel. Then in order to 
produce a variable cut-off a separate cut-off valve must be pro- 
vided. This is the object of the riding cut-off. The main valve 
determines the lead, point of release and point of exhaust closure 
and as the travel of the main valve relative to the crank is un- 
changeable these functions always remain the same. The duty of 
the cut-off valve is simply to close the ports in the main valve, 
and it determines the point of cut-off only. It will be seen, there- 
fore, that with this arrangement of valves, constant lead, exhaust 




/ 




opening and constant compression are secured while the point of 
cut-off is constantly changing with the load. Keeping these fun- 
damental facts in mind, it is readily seen that the main valve of 
the riding cut-off is, in operation, exactly the same as the ordi- 
nary D slide valve having a fixed travel. In the riding cut-off 
the travel of the cut-off valve is fixed, so far as length of stroke 
is concerned, but the times of closing the ports in the main valve 
are variable and are determined either by hand adjustment or by 
the governor, depending upon whether the engine is a throttling 
or an automatic cut-off engine. The points of cut-off are 
changed by rolling the cut-off eccentric around on the shaft. 



HANDBOOK ON ENGINEERING. 



247 



The farther the cut-off eccentric is set in advance of 
the crank the earlier in the stroke will steam be cut off, 
and, the nearer together the two eccentrics are set, the later 
will the cut-off occur. The main valve is generally designed 
to cut off steam at § or J stroke, so that if the cut- ' 
off valve and main valve move together the point of cut-off 
will be determined by the main valve and will occur at -| or 
J stroke. Now if the cut-off eccentric (c) be set ahead of 
the main eccentric (m) as in Fig. 7, it will reach the end of its 
stroke and start back again before the main eccentric has com- 
pleted the stroke, thus the cut-off valve moves in one direction 
and the main valve in the opposite direction and that point in the 
piston stroke at which the centers of the two valves meet will be 
the point of cut-off. If the cut-off eccentric be set nearly oppo- 
site the main eccentric it is evident that when the main valve 
reaches one-half of the outward stroke the cut-off \?alve will have 
reached nearly one-half of the return stroke and the cut-off will 
occur at about this point in the piston stroke, which will be 
approximately one-fourth stroke. 




Fig 8 



When setting the valves, first equalize the port opening of the 
main valve. This is accomplished by turning the main eccentric 
from one extreme position to the other seeing that both ports in 
the valve seat leading into the cylinder are opened exactly the 
same amount. It is not necessary that these ports be opened 
exactly wide ; the object is to see that both ports are opened to 
the same extent when the eccentric is in its extreme positions. 



248 HANDBOOK ON ENGINEERING. 

Having equalized the travel of the main valve place the crank on 
the dead-center, see page 195, and turn the full side of the main 
eccentric to a corresponding position. Then turn the eccentric 
in the direction the engine is to run until the port in the main 
valve, corresponding to the position of the crank or piston, opens 
the port leading into the cylinder to the amount of the lead, which 
may be taken as -gL- inch. Now, before moving the engine make 
a gauge of the form shown in Fig. 8. Put a punch mark on the 
stuffing-box, and, placing one end of the gauge in this mark, draw a 
fine line on the valve stem at the opposite point of the gauge. 
Turn the crank to the opposite dead-center and note the amount 
of lead opening. If it is not the same as first obtained adjust the 
eccentric rod to the extent of one-half the difference. Then place 
the gauge in the punch mark on the stuffing-box and draw a fine 
line at the opposite point of the gauge. 

Turn the crank back again to its first position and note the 
lead. If it is found to be equal at both ends, apply the 
gauge again and this time make a light punch mark at the outer 
point of the gauge. Then put a similar punch mark on the fine 
line representing the lead at the opposite end of the valve travel. 
By means of these marks it will be possible to set the main valve 
correctly without removing the steam chest cover. Now divide 
the distance between the two punch marks and put a third punch 
mark at the middle. Turn the crank around in the direction 
the engine is to. run until the middle punch mark falls under the 
outer point of the gauge. The main valve will now be at the 
middle of its travel. The travel of the cut-off valve must now be 
equalized so that the latter valve will travel equal distances be- 
yond the ports in the main valve. This is accomplished in pre- 
cisely the same manner as with the main valve. Having 
equalized the travel of the cut-off valve, turn the crank in the 
direction the engine is to run until the cross-head reaches the point 
in the stroke at which the cut-off is to occur, which is to be de- 



HANDBOOK ON ENGINEERING. 249 

signated by a line drawn on the guide. Now turn the cut-off 
eccentric in the same direction until it reaches its extreme position. 
Continue to move the eccentric until the cut-off valve just closes 
the port in the main valve. Secure the cut-off eccentric to the 
shaft at this point. Then turn the crank around until the cut- 
off takes place on the return stroke and see if it corresponds to 
the point on the previous stroke. If not, adjust the length of 
the cut-off eccentric rod an amount equal to one-half the differ- 
ence. 

It is important to be able to set the cut-off valve also without 
taking off the steam chest cover. One punch mark only is re- 
quired for this. Place the main valve in its position of mid- 
travel by means of the gauge. Then put a punch mark on the 
stuffing-box of the cut-off valve stem and, placing the gauge in 
this mark, put another at the opposite end of the gauge on the 
cut-off valve stem. See Fig. 8. 

This method furnishes a simple and quick means of setting 
both the main and cut-off valves when an eccentric slips. All 
that is necessary is to place the crank on the dead-center and 
bring the proper punch mark under the point of the gauge. Then 
bring the main valve to its position of mid-travel and with the 
gauge bring the cut-off valve to its proper position. 

The foregoing directions for setting the cut-off eccentric apply 
to the hand-adjusted gear only. When the cut-off eccentric is 
operated by the governor, the travel is equalized in precisely 
the same manner as when hand-adjusted. After equalizing the 
travel of the cut-off valve, place the crank on the dead-center. 
The main valve, which is invariably set first, will now open the 
port, corresponding to the position of the piston to the extent of 
the lead. Next block out the governor weights against the stops. 
Turn the full side of the cut-off eccentric to correspond to that of 
the crank as a starting-point. Then turn the cut-off eccentric 
(governor wheel), around on the shaft in the direction the engine 



250 HANDBOOK ON ENGINEERING. 

is to run until the port in the main valve is opened to the extent 
of the lead. Secure the governor wheel to the shaft. Turn the 
crank to the opposite dead-center and see that the cut-off valve 
opens the port in the main valve to the same extent. If the 
difference is slight it may be equalized by adjusting the length 
of the cut-off eccentric rod an amount equal to one-half the differ- 
ence of the lead openings. Should the difference be great, say, 
one-half inch, that is, should the cut-off valve lack one-half inch 
of opening the port in the main valve, it indicates that the cut-off 
valve is too long, which is apt to be the case where two cut-off 
valves are employed on the same stem. The valve may be 
shortened by moving the two parts closer together, moving each 
part one-fourth of the amount the cut-off valve lacked of opening 
the port in the main valve. Then begin over again to set the 
cut-off eccentric and if the adjustments have been carefully made 
it will open the ports correctly at both ends of the main valve. 
After fastening the main eccentric and the governor wheel securely 
to the shaft remove the blocks from the governor weights and the 
job will be finished. 

When the valve gear contains a rocker-shaft of the construc- 
tion shown on page 322, the eccentric must be turned in the 
opposite direction to that in which the engine is to run, until the 
main valve opens the port leading into the cylinder, to the extent 
of the lead. 



HANDBOOK ON ENGINEERING. 251 



CHAPTER XII. 

THE STEAM ENGINE, — Continued. 

Work consists of the sustained exertion of force through space. 
The unit of work, the foot-pound, is a force of one pound exerted 
through one foot space. The work done in lifting one pound ten 
feet, or ten pounds one foot, is ten-foot pounds. 

Power is the rate of work, or the number of foot-pounds ex- 
erted in a unit of time. The unit of power is the horse-power, 
and equals 33,000 foot-pounds exerted in a minute, or 550 foot- 
pounds exerted in a second, or 1,980,000 foot-pounds exerted in 
an hour. An engine developing fifty-horse power, exerts 27,500 
foot-pounds per second, 1,650,000 foot-pounds in a minute. It 
could raise (friction neglected) 41,250 pounds forty feet in one 
minute. 

A belt running over a pulley at 4,000 feet per minute, pulling 

with a force of 240 pounds (fair load for a 4-inch belt) will 

transmit 

240x4,000 

— oo nrin — equal thirty horse-power (nearly). 

If moving at 1,100 feet per minute, the result would be 

240x1,100 

— aa nnn — equal eight horse-power. 

A gear-wheel, the cogs of which transmit a pressure of 1,800 

pounds (fair load for 1J" pitch 6" face) to the cogs of its mate, 

the periphery velocity of the wheels being ten feet per second, 

transmits 

1,800x10 
k^ equal thirty-three horsepower nearly. 



252 HANDBOOK ON ENGINEERING. 

If speed was 360 feet per minute, it would transmit 

1,800x360 

— oo nnr> equal twenty horse-power nearly. 

The horse-power developed by a steam engine consists of two 
primary factors, Piston Speed and Total Average Pressure of 
steam upon the piston. 

Piston speed depends upon the stroke of engine and the num- 
ber of revolutions per minute. An engine with stroke of twelve 
inches, making 300 revolutions per minute, has a piston speed of 

2 x 12 x 300 

r^ equal 600 feet per minute. 

Piston speed of an engine with 24" stroke at 150 revolutions 

per minute : 

2x24x150 

zr^ equal 600 feet per minute. 

Total average pressure depends on area of piston and mean 
effective pressure per square inch exerted on piston throughout 
stroke. The mean effective pressure (M. E. P.) in any case can 
only be accurately obtained by means of the steam engine indi- 
cator, and depends upon the load engine is carrying. 



GENERAL PROPORTIONS. 

Diameter of steam pipes : 

Slide-valve engine, J diameter of piston. 
Automatic high-speed engines, i diameter of piston. 
Corliss engine, t 3 q diameter of piston. 

Diameter of exhaust pipes : 

Slide-valve engine, i diameter of piston. 
Automatic high-speed engine, § diameter of piston, 
Corliss engine, i to | diameter of jjiston. 



HANDBOOK ON ENGINEERING. 253 

Displacement of piston 

Clearance spaces: in °ne stroke. 

Slide-valve engine 0.06 to 0.08 

Automatic high-speed engine, single valve . 0.08 to 0.15 

Automatic high-speed engine, double valve . 0.03 to 0.05 
Automatic cut-off engine, Corliss type, long 

stroke 0.02 to 0.04 

Weights of engines per rated horse-power : 

Slide-valve engine 125 to 135 lbs. 

Automatic high-speed engine 90 to 120 lbs. 

Corliss engine . 220 to 250 lbs. 

Fly- wheels, weight per rated horse-power : 

Slide-valve engine 33 lbs. 

Automatic high-speed engine 25 to 33 lbs. 

(According to size and speed.) 
Corliss engine 80 to 120 lbs. 

(According to size and speed.) 

RULES FOR FLY=WHEEL WEIGHTS, SINGLE CYLINDER 
ENGINES. 

Let d = diameter of cylinder in inches. 

S = stroke of cylinder in inches. 

D = diameter of fly-wheel in feet. 

M = revolutions per minute. 

W= weight of fly-wheel in pounds. 

d 2 S 
For slide-valve engines, ordinary duty . W= 350,000 ™ ™ 

d 2 S 
For slide-valve engines, electric lighting. W= 700,000 y^n™ 

d 2 S' 
For automatic high-speed engines . . W= 1,000,000 y, 2 „ 2 



254 HANDBOOK ON ENGINEERING. 

d 2 S 

For Corliss engines, ordinary duty . . TT= 700,000 m m 
For Corliss engines, electric lighting . W= 1,000,000 ^ „ 




The Russell Engine, 

SETTING THE VALVE ON A RUSSELL ENGINE, SINGLE VALVE 
TYPE. THE SAHE PRINCIPLE LAID DOWN IN THE 5ET= 
TING OF THE COilMON SLIDE VALVE MUST BE ADHERED 
TO. 

The style of valve is shown in cut, Fig. 1. It is, to some 
extent, a moving steam chest with the steam all within itself , 
admitting only enough steam into the chest to keep the valve to 
its seat, against the maximum tendency to leave it. This pres- 
sure in the chest is found with the valve as at present propor- 
tioned, to be about 45 per cent of that contained within the 
valve. The cut shows the valve and section of cylinder so 
plainly as to render any detailed explanation of same almost 
unnecessary. 



HANDBOOK ON ENGINEERING. 



255 



The eccentric operating the valve is under control of the gover- 
nor, as shown in cut Fig. 2, which regulates the speed of the 
engine by sliding the eccentric across the shaft, either forward or 
backward, as the weights change their position, thereby cutting 
the steam off earlier or later in the stroke, as the governor, or 
more properly, the weights adjust themselves to the load. 

When the eccentric is moved across the shaft in a direction 
that reduces its eccentricity, the steam is cut off earlier in the 




FIG-. 1) 



stroke; when the eccentric is moved in the opposite direction, 
the steam is cut off later in the stroke. The extreme range of 
this cut-off is from to f of the engine's stroke, and this 
whole range of adjustment is under complete control of the 
governor. 

To preserve a certain determined speed with the smallest pos- 
sible variation, as changes occur in the load or pressure, is the 
function of the governor. The cut-off must always be propor- 
tioned to the load. When the engine is running empty, the steam 
is cut off at the beginning of the stroke and the governor weights 
are at their extreme outer position. With a heavy load, steam 
follows further and the weights are nearer their inner position. B.e- 

16 



256 HANDBOOK ON ENGINEERING. 

tween these two limits, any number of positions of the weights, and 
corresponding angular positions of the eccentric, may be had ; and 



Fig. 2. 

as the steam is thus adapted to the load in each position, it follows 
that a slight increase or decrease in speed must make a change in 
the cut-off and bring the engine again to standard speed. 



HANDBOOK ON ENGINEERING. 257 

In setting the valves it is necessary to mark the ports in the 
valve face at the outer edge of the steam chest, and also to mark 
on the back of the valve the ports in its face, so that it may be 
adjusted after being placed in the chest, in which position it pre- 
sents a blank surface that, without these marks, would afford no 
means for knowing its position. 

In placing the valve in the chest, see that it fits perfectly 
against the seat and that the bottom bearing, on which the valve 
rides, is at right angles to the valve seat, and in such a condition 
that the valve will not be tipped away from its seat, but rather 
against it. This latter condition will be insured by easing off 
the bottom- strip at the inner corner, so that the valve would 
bear hardest at the outer edge. The hinge nut, into which the 
valve stem is screwed, as well as its trunnion bearings, should 
fit so that the valve lays closely to its seat, rather than be held 
away from it. 

Having" extended the marks of the ports as well in the valve 
seats as in the valve itself, to the outside, it now becomes neces- 
sary to get the center of the travel of the eccentric and connect 
the valve and rod, so that the valve will travel equally on either 
side of this center. The throw of the eccentric leads the crank in 
the direction the engine runs, and with the eccentric properly 
located, as it cannot help being, because it is attached to the 
governor and the governor is keyed to the shaft, the lead will 
remain the same with the governor weights in their outer as well 
as in their inner positions. 

These valves are usually marked with the engine on the center 
at either end, marks corresponding with the admission edges of 
valve and seat. The hinge nut connection makes it convenient to 
examine these valves without disconnecting or disturbing any 
adjustments made. The valve rod has right and left-hand threads 
for adjustment, and final adjustment can be made without taking 
off the steam chest cover. 

17 



258 



HANDBOOK ON ENGINEERING. 




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HANDBOOK ON ENGINEERING. 259 

THE PORTER=ALLEN STEAM ENGINE, MADE BY THE 
SOUTHWARK FOUNDRY & HACHINE CO. 

This engine claims the distinction of being tbe original and 
most perfect type of the high-speed steam engine. In truth, 
however, it should not be termed a high-speed engine. Relatively, 
indeed, to those speeds to which it has hitherto been found neces- 
sary to limit the motion of engines, its speed is high ; but consid- 
ered absolutely, and as it appears to all persons accustomed to it, 
this engine is ordinarily run at what is undoubtedly the natural, 
and on all accounts, the desirable speed at which a properly 
designed and constructed steam engine ought to be run, for ordi- 
nary purposes ; while this is much below the speed of which it is 
capable, and at which it is run with entire success, in cases where 
'such speeds are required. This engine is presented as one which, 
distinguished by a system of valves and valve movements per- 
fectly adapted to improved rotative speed, has also been designed 
upon sound principles, and is made in the most excellent manner ; 
so that, without the least drawback, all the advantages of this 
speed may be realized by the use of it. A description of this 
engine naturally commences with the valve gear and valves. 

Its central feature is a link actuated by a single eccentric, 
from which separate and independent movements are given to the 
admission and the exhaust valves. 

Attention is first invited to 

The position of the eccentric* — The eccentric is placed on the 
shaft in the same position with the crank, and cannot be altered 
from this position. The lead of the valves is adjusted by other 
means. The first requirement of this system is, that the crank 
and the eccentric shall have coincident movements, and so shall 
arrive on their dead points, or lines of centers, simultaneously. 

To insure the permanence of the eccentric in its correct posi- 
tion, and also for compactness, and as a superior mechanical con- 



260 



HANDBOOK ON ENGINEERING. 



str action, it is formed in one piece with the shaft, and its low 
side is brought down to the surface of it, as shown in Fig. 1. 

The link* — The construction of the liuk is also shown in 
Fio-. 1. It is of the form known as stationary link, and con- 
sists of a curved arm, partly slotted, formed in one piece with tbe 
eccentric strap, and pivoted at its middle point on trunnions, which 




Fig. 1. 

vibrate in an arc whose chord is equal to the throw of the eccen- 
tric, about a sustaining pin secured rigidly to the bed. The 
radius of the link is equal to the length of the first rod, by which 
its motion is communicated to the admission valves. 

In the slot is fitted a block from which the admission valves 
receive their motion. This block is moved by the action of the 
governor, which thus varies the point of cut-off. If the center 
of the block is brought to the center of the trunnions, the port is 
not opened at all, except by the lead given to the valves, and this 



HANDBOOK ON ENGINEERING. 261 

opening is closed before the piston has advanced a sensible 
amount. If, on the other hand, the block is brought to the end 
of the slot, as here represented, the steam is not cut off until the 
j)iston has reached about six-tenths of the stroke, which is the 
limit of the admission. 

The exhaust valves are driven from a fixed point on the link, 
and have, of course, an invariable motion. The movements of 
the link at this point are admirably suited to this function, caus- 
ing the steam, wherever it may have been cut off by the admis- 
sion valves, to be held until near the termination of the stroke, 
when it receives a free and ample release, and is confined again 
near the end of the stroke by the closing of the exhaust valves at 
a point which provides the compression required to arrest the 
motion of the reciprocating parts, and at the same time, fill the 
end clearance of the cylinder with the compressed steam. 

The peculiar motion of the link is given to it by a combination 
of the horizontal and the vertical throws of the eccentric. The 
horizontal throw alone only moves the link from one to the other 
of the lead lines, which motion only draws off the lap of the 
valves. The opening movement is produced by the tipping of the 
link alternately in the opposite directions beyond the lead lines, 
and these tipping motions are given by the vertical throws of the 
eccentric. Its upward throw tips the link in the direction from 
the shaft and opens the port at the further end of the cylinder ; 
and its downward throw tips the link towards the shaft, and 
opens the port at the crank end of the cylinder. At the same 
time, its horizontal throw is drawing the valve back, and when in 
this return' movement, that point in the link at which the block 
stands, crosses the head -line, the steam is cut off. 

This link possesses a distinguishing excellence, which will 
now be described* — The angular vibration of the connecting rod 
causes a considerable difference in the motion of the piston in 
the opposite ends of the cylinder, retarding it in the end 



262 HANDBOOK ON ENGINEERING. 

nearest to the crank, and accelerating it at the end farthest from 
it. When the length of the connecting rod equals six cranks, as 
is usually the case, this difference in velocity averages 20 per 
cent, and at the commencement and termination of the strokes, 
reaches the great amount of forty per cent. 

The driven arm of the link is of such length that its angular 
vibration coincides in degree, as well as in time, with those of 
the connecting rod ; and so the trunnions of the link receive a 
motion coincident with that of the piston, and the link gives to 
the valves, in opening and closing their ports, different velocities, 
accelerated at one end of the cylinder and retarded at the 
other, corresponding to the difference in the velocity of the 
piston. 

Difference of lead* — The application of this gear to the 
engine under an adjustment provides for a slight difference in 
lead at either end of the stroke, and the amount of this dissimi- 
larity is in the direct ratio as the variation of the piston velocities 
at the end of the stroke. 

The manner in which the link imparts to the exhaust 
valves their movements* — The exhaust valves open and close 
their ports in such manner that the opening is made while the 
valve is moving swiftly, and one-half of the opening movement 
has been accomplished when the piston arrives at the end of its 
stroke. The valves are so constructed that this portion of the 
movement opens the whole area of the port, which does not begin 
to be contracted again until the center line of the link has re- 
crossed the lead lines on its return. The speed of the piston is 
then also diminishing, and the exhaust is not throttled at all 
until the port is just about to be closed. 

The differential valve movement* — A wrist motion is intro- 
duced into the connection of the admission valves. 

In this movement, an arm which is connected by a rod with 
the block in the link, communicates through a rock shaft, motion 



HANDBOOK ON ENGINEERING. 263 

to the two otlief arms, causing them to vibrate in the same verti- 
cal plane in which the valves move. Each of these arms alter- 
nately rises nearly to the vertical position, while the other, at the 
same time, descends to and beyond its dead point. 

Each by a separate connection, imparts motion to one of the 
dmission valves, and at the top of its vibration causes it to open- 
and close its port swiftly and then, descending to its idle arc, 
reduces the motion of the valve to an interval practically of rest. 

These movements can be followed in the cut where the upper 
arm is about to move in its arc to the left, and thus, through the 
lower connections, to open the port at the further end of the 
cylinder, while the lower arm will be scarcely moving in its valves 
at all. In this manner, the width of opening is largely in- 
creased, chiefly by a difference in the length of the levers, while, 
at the same time, fully one-half of the lap, or the useless motion 
of each valve after it has covered its port, is got rid of, so that 
smaller valves and narrower seats are employed, and notwith- 
standing the greater opening movement, the total motion of the 
valves is very much reduced. 

THE ADJUSTABLE PRESSURE PLATES. 

Description of these plates* — The construction of these pres- 
sure plates and the method of adjusting them are fully represented 
in the sections of the cylinder, Figs. 2 and 3. 

On the lower side of the horizontal section, Fig. 2, both 
admission valves are shown, working between their opposite 
parallel seats, one of which is formed on the cylinder, and the 
other on the pressure plates, the latter having cavities opposite 
the ports. 

The valve at the further end of the cylinder is at the 
extremity of its lap, while the one at the crank end has com- 
menced to open the four passages for admission of the steam. 



264 



HANDBOOK ON ENGINEERING. 



The vertical cross-section, Fig. 3, passes through the middle 
of one pressure plate and shows its form and the means 
employed for its adjustment. It is made hollow and most of 




hsr- 



Fiar. 2. 



the steam supplied to two of the openings passes through it. 
It is arched to resist the pressure of the steam without deflec- 
tion. It rests on two inclined supports, one above and the 
other below the valve. These inclines are steep, so that the 
plate will be sure to move freely down them under the steam 
pressure, and also that it may be closed up to the valve with 
only a small vertical movement. It is prevented from moving 
down these inclines by a screw, passing through the bottom 
of the chest, the point of which, as also the plug against which 
it bears, is of hardened steel. 

The pressure plate is held in its correct position by projections 
in the che«t, on one side, and tongues projecting from the cover 
on the other, which bear against it near each end, as shown. 



HANDBOOK ON ENGINEERING. 



265 



Between these guides, it is capable of motion up and down its 
inclined supports, and also directly back and forth between the 
valve and the cover. 

The pressure of steam is always on this plate, and tends to 
force it down the incline to rest on the valve. By means of 
the screw it is forced against the steam pressure, up the in- 
clines and away from the valve. This adjustment is capable of 
great precision, so that the valve works with entire freedom 
between its opposite seats, and still is steam-tight. 

How these plates act as relief valves, — Whenever the pres- 
sure in the cylinder exceeds that in the chest, the admission 




Fig. 3. 



pressure plate is instantly moved back to contact with the cover, 
thus affording an ample passage for the discharge of water 
before it can exert a dangerous strain. This plate is superior 



266 



HANDBOOK ON ENGINEERING. 



in this action to any of the ordinary forms of relief valve, both 
in the area opened, and also in being self-adjusted to the pressure, 
and opening fully the instant that is exceeded. 

How to keep the admission valves tight* — These valves, 
though moving in complete equilibrium, are liable to slight wear. 



102 nc yCOi'- O, 




iQi rm«. rrn 




This should be taken up as it appears, by letting down the 
pressure plates. The construction of these plates and the method 
of adjusting them, are shown in the accompanying sections, made 
through the steam chest at one end of the cylinder. Of these, 
Figs. 1 and 2 are horizontal sections, showing the four-opening of 



HANDBOOK ON ENGINEERING. 



267 



the valve — first, when commencing to open, with arrows indicating 
the course of the steam ; and, second, at the extreme point of its 
lap; while Figs. 3 and 4 are vertical sections, showing the 




pressure plate — first, when by turning the bolt d forward it is 
forced up the inclines and away from the valve, producing aleak ; 
and second, when it is let down to its proper working position. 
A is the port, B the valve, and C the pressure plate. The latter 




i3 made with a trussed-back and so cannot be deflected by the 
steam pressure. Through the passage thus formed, the steam 
reaches two of the openings. 



268 HANDBOOK ON ENGINEERING. 

The pressure plate rests on two inclined supports, e, c, and 
the pressure of . the steam forces it down these inclines as far 
as the bolt d underneath will allow. This bolt holds the plate 
just off from the. valve, so that the latter moves freely, 
and is still steam tight. Whenever leakage appears, a minute 
turning of this bolt backwards lets the pressure plate down and 
closes it. 

Provision is made for readily detecting the least leakage, as 
follows : When the engine is warmed up in its normal working 
condition, open the indicator cocks, or in the absence of these, 
remove the plugs from the top of the cylinder, unhook the link 
rod, and set the valves by the starting bar so that both ports are 
covered, and turn on the steam. If the valve leaks at the eud of 
the cylinder, which is not then open to the atmosphere or the 
condenser, the steam will blow out at the opening provided, having* 
no other outlet. ■ Then let down its pressure plate by backing the 
bolt very carefully till the leak disappears. The valve should 
still move freely when the leak has disappeared, and the pressure 
plate must not be let down any closer than is necessary for this 
purpose. 

Leakage at the opposite end of the cylinder will not generally 
be seen, the steam escaping* freely by the open exhaust. To test 
its valve in the same manner, the engine must be turned on to the 
opposite stroke. These examinations should be made from time 
to time. 

In the small engines which have no starting bar, the valve rod 
can be disconnected and moved by hand to test this point. 

An engine should never be started till it is warmed up. The 
valves warm quicker than the supports on which the pressure 
plates rest, and are tight between their seats by expansion, until 
the temperatures have become nearly equalized. Provision for 
detecting and stopping any leak of steam is the crowning 
excellence of this valve. 



, HANDBOOK ON ENGINEERING. 269 

These valves are small and light ; each admits and cuts off 
the steam simultaneously at four openings ; each works in com- 
plete equilibrium ; their line of draft is central, so that unequal 
wear is entirely avoided. 

To set the admission valves* — Place the engine on one of its 
dead centers as explained on page 195. Then raise the governor, 
bringing the center of the block between the centers of the 
trunnions of the link. 

With the g-overnor remaining up, set the valve that is about 
to open, giving to it a lead of f rom T ^ " to T 3 ^ " , according to 
the size of the engine. High speed requires considerable lead. 
Repeat this for the other valve on the opposite center. 

On letting" the governor down, the crank remaining on the 
dead center, it will be seen that the valve is moved a short dis- 
tance. This motion of the valve, produced by moving the block 
from the trunnions to the extremity of the link while the crank 
stands on the center, is the same in amount on either center and 
takes place in the same direction ; namely, towards the crank. 
Its effect is, therefore, to cover the port nearest the crank and to 
enlarge the opening of the port farthest from it ; so that the lead, 
which is equal at the earliest point of cut off, is at the crank end 
of the cylinder gradually diminished, and at the back end increased 
in the same degree as the steam follows further. 

The effect of this is to equalize the opening and cut-off move- 
ments, so that, on setting the governor at any elevation whatever 
and turning the engine over, the openings made and the points of 
cut-off will be found to be identical on the opposite strokes, from 
the commencement up to the maximum admission. This differ- 
ence in the lead is also singularly adapted to the difference in the 
piston velocity at the two ends of the cylinder. 

In case the indicator shows that the lead of either admission 
valve requires to be changed, this is done without opening the 
chest, by lengthening or shortening the stem at the socket of 



270 HANDBOOK ON ENGINEERING. 

its guide, bearing in mind that each valve moves towards the 
middle of the eyclinder to open its port. 

To set the exhaust valves* — These have an invariable motion, 
and are admirably adapted to their purpose. They are set so as 
to open before the end of the stroke enough to give ample lead, 
and close again when the piston is on the return stroke, early 
enough to effect the required compression. 

All the valves are held between pairs of brass nuts, of which 
the inner one is flanged. These nuts must be securely locked, 
and should be so set upon the valve that it is free to adjust itself 
between the nuts while yet sufficiently tight that no ' ' lost motion ' ' 
exists. To avoid the consequences of a mistake, care should be 
taken, before closing the valve chests, to turn the engine slowly 
through an entire revolution, while the movements of the valves 
are carefully watched, so as to insure that they have not been so 
set as to bring the valves or their nuts into contact with the ends 
of the chest at the extremes of their movements. 

The governor* — The Porter Governor, original in its type, 
stands unexcelled as adapted to stationary engines, requiring close 
regulation. The active parts are very light, the power being 
derived from a high rotative speed, causing a sensitiveness in its 
movements that will arrest fluctuations and produce uniformity in 
the running of the engine. It has been so perfected that at the 
present day it is easily adapted to the requirements of any class 
of work necessitating a governor, and is especially desirable for 
an engine where a steady speed is necessary. 

The speed of this governor being constant, makes it equally 
efficient upon an engine running either at a high or low number 
of revolutions. That is to say, the speed of engine can be 
altered from time to time by changing the governor pulley, the 
governor itself continuing to run at the same speed and under the 
same strains, and being stationary, it is always open to observa- 
tion. Whereas, any change in speed of engine with the wheel or 



HANDBOOK ON ENGINEERING. 271 

shaft governor, increases or decreases the initial strains upon all 
the parts of the governor, and they have to be adjusted accordingly. 

It is manufactured and sold separate from the Porter- Allen 
engines. 

How to tighten the side boxes of the main bearing* — This 
is done by drawing up the wedge with the bolts by which it is 
suspended from the cap. The time to do this is when the engine 
is running and the freedom of the journal between its side boxes 
can be felt. The engineer can then draw up the wedges to take 
this out as much as he deems prudent. 

DIRECTIONS FOR SETTING AND RUNNING THE PORTER= 
ALLEN STEAM ENGINE. 

The foundation* — This should be made of concrete, hard 
bricks or stone laid in cement. Bricks are preferred on account 
of their rectangular form and of the more perfect bond they 
make with the cement. Stones of irregular form are sure to have 
the cement bond broken and to spread under the strain of the 
bolts. The bricks should be wet, and the cement washed into 
every course. 

Time should be allowed for the cement to set before any weight 
is put upon it. A week, at least, is required for this purpose ; a 
month is none too long. 

Heavy cut stone is ornamental for a coping, but not essential 
where there is a bed-plate ; the bed-plate of an engine being not a 
mere name, but a reality 

A foundation plan for locating the bolts should be made for each 
engine. The bolts should have some play in the masonry. The 
best way of insuring this is to inclose each bolt in a wooden box 
of half -inch stuff, about sixteen inches long, which is drawn up 
as the courses are added and removed entirely before the engine 
is placed on the foundation, so the bolt holes may be poured full 
of cement after the setting is completed. 



272 HANDBOOK ON ENGINEERING. 

Under ordinary circumstances, a foundation built to the plan 
furnished is ample to hold the engine still ; but wheu it must he 
builton soft ground, or on sand or loose gravel, or must be carried 
up through abasement or cellar, it should be extended at the base 
lengthwise in each direction. Sometimes, both these obstacles to 
stability are met with, when the foundation should be extended as 
far as practicable, and at one end, at least, tied to a wall quite 
up to the engine-room floor. The builders of the engine should 
be consulted in such cases. 

Setting the bed. — This setting is done iu the usual manner, 
by a line through the cylinder, which is bolted at the end of the 
bed in alignment with the guides. In case the cylinder is not 
yet in place, it is represented by the bore in the head of the bed, 
and the line is to be continued midway between the side rails of 
the lower guide bars. 

The guides lie in one plane and are to be used for leveling the 
bed in both directions. 

The base of the bed is not brought in contact with the founda- 
tion. Thin parallel packing pieces are to be placed on each side 
of each bolt and under each end of the main bearing, and the bed 
must bear equally on all these, when the guides are level in all 
directions, before any strain is put on the bolts. After these have 
been tightened and the guides are finally found to be level, the 
broad flange of the bed is brought to a general bearing on the 
foundation, by running sulphur under it, or by caulking with 
iron borings wet with water made only slightly acid with sal- 
ammoniac. 

Setting the shaft. — In placing the shaft in position, three 
requirements must be observed. First, to place it at a right 
angle with the axis of the cylinder. Second, that it shall be level. 
Third, that it lies fairly in its bearings. It is readily squared. 
The crank disc is finished on the shaft centers after the 
pin has been set, so that its rim is on the opposite side equally 



j 



HANDBOOK ON ENGINEERING. 273 

distant from its center line, the shaft is square. It is leveled by 
plumbing the crank disc. When thus set it will lie fairly in the 
main tearing ; and if the outer bearing has been correctly set, it 
will lie fairly in that also. This is tested by rotating the shaft 
entirely dry. Brightened rings will show what parts of the 
journals have found bearings, and on lifting the shaft, bright 
spots on the babbitt metal will show where these bearings were. 

The boxes are slightly larger than the journals and so the lat- 
ter should bear along the center of the lower box and not on the 
sides. 

The journals of the shaft if set as here directed will, with 
ordinary lubrication, run cold from the start. Should the shaft 
ever get out of line, it ~may be squared by gauging between the 
rim of the crank disc and bosses provided on the bed. 

SPECIFICATIONS FOR CENTRALLY BALANCED CENTRI= 
FUGAL INERTIA GOVERNOR. 

It is difficult to say just what is the most important part of 
a modern steam engine, but certainly its governor is among the 
very first. Here then is my idea of what they should be : — 

First. The governor must so regulate the speed of the engine's 
revolutions that when starting or stopping it shall not " pound " 
or knock, which means some danger, considerable wear and much 
annoyance. 

Second. It must so regulate the engine's speed when in service, 
that when 125 per cent of its rated capacity be instantly thrown 
upon the engine, the change in speed will not be more than 11 per 
cent greater or less than the constant speed ; and that if the same 
load be instantly thrown off the engine, the variation shall, in that 
case, be no greater than one per cent. 

Third. That the governor must show every evidence of stability 
or ability to have all descriptions of break loads thrown on or off, 

18 



274 HANDBOOK ON ENGINEERING. 

or both, without " racing " or " weaving " beyond li per cent of 
constant speed. This is to insure against accident and expert 
assistance. 

Fourth. Should any part of the governor or its attachments 
break or become disconnected, the device must not do otherwise 
than to bring the engine to a full stop. 

Fifth. All the parts of the governor must be light, yet of finest 
materials, to save wasted energy and yet insure reliability. 

Sixth. The construction must be such that during all ranges of 
cut-off, the parts shall remain at all times in perfect balance. 
" Out-of -balance " almost more than any other one difficulty 
has prevented the full success of wheel governing engines, there- 
fore, this feature must be eliminated. No device obviously inca- 
pable of constant balance should be considered unless that long 
sought and potential factor of line running is to be sacrificed with 
open eyes. 

Seventh. All parts subjected to transmitting strains must be of 
steel. 

Eighth. All transmitting bearings must be provided with 
hardened and ground to gauge steel pins, each of which must be 
furnished with movable phosphor bronze bushings to save wear 
and enable quick and interchangeable repairs. 

Ninth. Springs must be of best quality and made with screwed 
"plug" connections. The bending of the spring into hook or 
eye for connecting will not be permitted. 

Tenth. Governor must be so designed and provided with mov- 
able weights, that the speed may be diminished or increased 
graduated amounts without disturbing otherwise the adjustment 
of the mechanism. 

Eleventh. Any governor so designed as to accomplish regula- 
tion clause primarily, and at the same time fulfills all other 
requirements will naturally receive preference over other devices, 
which evidently fairly accomplish regulation but fail in other 



HANDBOOK ON ENGINEERING. 



275 



expectations, and yet apparently have only lower first cost as a 
defense. 

The Armington and Sims Engine, as is well known, is of the 
high speed type, and in its earlier form was designed with double 
eccentrics, one inside of the other. These eccentrics are operated 
by the shaft governor, and the compound motion produced by the 
movements of the two eccentrics is such that the valve has equal 
lead for all points of cut-off. 




Valve Gear of the Armington & Sims Automatic Engine 



The method of setting the valve is very simple, for all engines 
of this make are sent out with the valve stem and slide marked at 
points C and B in the sketch, and these points should be set just 
three inches apart. The following are the directions which the 
builders supply : — 

" If the distance between B and G is just three inches you will 
know that the valve is all right. If, however, you wish to put in 
a new valve and adjust, then remove the steam-chest cover and 
place the engine on the center as follows : Place line marked A, 
which is on the crank pin side, with line on opposite side of rim 
marked F (not shown in drawing), level with engine; now take 
out, or loosen up the springs and block the weights out so that 
the distance betwee^weights and pin at D E will be J of an inch ; 
adjust the valve-stem at the guide so that by turning the engine over 



276 



HANDBOOK ON ENGINEERING. 



from one center to the other the lead will be the same at both 
ports ; then make a new mark distinctly on the valve- rod, so that 
the distance B C will be the standard three inches. 

" It is not possible to reverse the direction of running without 
sending to the factory for new parts. The governor is not con- 
structed so that one set of parts can be used for running both 
ways." 

THE CARE AND MANAGEMENT OF HARRISBURG ENGINES. 

It is essential to the successful operation of any high-class and 
expensive machinery, that the person in charge be gifted with a 
fair degree of intelligence and alertness, and while I have at- 
tempted to formulate a few rules as a guide to the person in 




Sectional Elevation of Harrisburg Standard Four-Valve 
Tandem Compound Engine. 



charge of an engine, the fact must not be overlooked that a great 
deal depends upon the skill and judgment of the operator himself, 
and that it is manifestly impossible to give rules other than of a 
general character and which may frequently have to be modified 
to suit the different conditions that may arise. However, the 



HANDBOOK ON ENGINEERING. 277 

following are some suggestions for the convenience of operating- 
engineers : — 

When engines of these styles have been properly erected, the 
steam, exhaust and drain connections completed, and the piston 
and valve rods packed, the operator should be careful to see that 
all parts are in proper position and firmly secured. 

The bed should be thoroughly cleansed inside and a good 
quality of machine oil poured into the reservoir beneath the crank, 
until it is just in contact with the crank disc. 

A mineral oil only should be used, and of medium viscosity. 
Fill the eccentric lubricating cup and flush the main bearings 
with the oil. 

The cylinder lubricator should be filled with a first-class qual- 
ity of cylinder oil, of heavy body. 

The best oils obtainable are the most economical, without 
question. 

Careful preparations before starting engine* — The cylinder 
and steam chest drain valve should now be opened, and the 
throttle valve carefully started just enough to allow a small quan- 
tity of steam to flow through the cylinder and out through the 
drain pipes, but not enough to actually start the engine in 
motion. 

After the cylinder and valves have been thoroughly heated 
and any water standing in the steam pipes thus blown off, start 
the oil flowing in the cylinder lubricator cup. A general survey 
of the engine should now be taken and if everything is found to 
be in proper condition, carefully open the throttle valve and bring 
the engine gradually up to speed, when it should be noted that 
the governor is controlling the machine. Examine the bearings 
and eccentric to see if the oil is flowing properly, and make sure 
that every part is operating smoothly, after which the drain valves 
may be closed. 

Adjustments for weai 4 * — When the engine has been in opera- 



278 HANDBOOK ON ENGINEERING. 

tion long enough to necessitate the adjustment of the working 
parts, care should be used to avoid adjusting them so close as to 
cause heating, and the following general rules should be 
observed : — 

The caps on the main bearings should always have sufficient 
liners underneath to enable the nuts on the bearing studs to draw 
the cap down solidly upon them and not pinch the shaft, which 
should be free to revolve in its bearings without unnecessary play. 

Adjustment of crank-end connecting rod, — In adjusting the 
connecting-rod box at the crank pin end the same general rules 
should be observed regarding the liners under the cap, the large 
nuts drawn solidly upon it, the small nuts firmly jammed, and 
the cotter pins placed in position. 

The adjustment of the box should then be tested with a lever 
about 12 inches in length, the adjustment being so made that 
with a lever of this length the operator can easily move the end of 
the connecting rod sufficiently to take up the side play between 
the flanges on the crank pin and the ends of the box. The 
adjustment should never be made so close that this side movement 
Cannot be observed. 

Adjustment of cross-head pin box. — The adjustment of the 
connecting-rod box at the cross-head pin end should be made by 
removing the name plate from the engine frame and placing the 
crank on the center nearest the cylinder, then with the wrench 
provided for that purpose, slack off both wedge screws at the 
upper and lower sides of the connecting rod, and draw the wedge 
up until it is solid against the box, then slack off that screw 
about a sixth of a turn and draw up the other so as to firmly lock 
the wedge ; this method prevents the box from pinching the 
cross-head pin. 

The " flats " on the cross-head pin should always be at the 
top and bottom to avoid wearing a shoulder, and the nut on the 
end should be drawn up firmly, but not so much as to spring the 



HANDBOOK ON ENGINEERING. 279 

bosses of the cross-head together, nor yet enough to make the 
box tight on the ends. 

I prefer adjustment of the cross-head in the guides made by 
liners of paper or tin, placed between the bronze shoes and the 
body of the cross-head. 

Adjustment of cross-head shoes* — In order to do this it is 
necessary to remove the pin and the end of the connecting rod 
from the cross-head, and with a wooden lever placed in the pin 
hole turn the cross-head until the shoes are out of the guides, 
then remove the shoes and place the liners beneath them. Care 
should be used that the cross-head does not fit the guides too 
closely, and that it can be moved freely with a short lever from 
one end of the guides to the other, while disconnected from the 
connecting-rod . 

The cross-head should never be run very close and should 
always be free enough to allow long and continuous runs without 
causing the top of the bed over the guides to feel uncomfortably 
warm to the touch. 

Attachment of cross-head to piston rod* — When making any 
adjustments of the cross-head, it is well for the operator to assure 
himself that the lock nut, which prevents the piston rod from 
turning in the boss at the end of the cross-head, is securely in place. 
All but the largest Harrisburg engines are tested under steam 
before leaving the works, and the valves set with the indicator. 

The distance from the cylinder head end of the valve, when 
the crank is on the center nearest the cylinder, is marked on the 
end of the cylinder directly underneath the steam chest cover. 
If from any cause the valve should become deranged, place the 
crank on the center described and with a scale or rule, see that 
the valve position corresponds to the dimension marked on the 
end of the cylinder; and if out of position, it can easily be re- 
adjusted by means of the device provided for that purpose, at the 
outer end of the valve stem. 



280 HANDBOOK ON ENGINEERING. 

On the Harrisburg Ideal Engines, where the ball joint con- 
nection is used between the valve stem and the eccentric rod, the 
wear is followed up by filing the end of the bronze connection 
that the cap is screwed against, which* holds the ball in place. 
And on the Harrisburg Standard Engines, where the ram box 
connection is used, the adjustment is made by filing the half of 
the bronze box, which is attached to the end of the eccentric rod 
that connects with the ram. 

Adjustment of eccentric strap* — The eccentric strap adjust 
ment is made by liners placed between the halves of the strap and 
double nutted bolts. When adjustment is necessary, the other 
end of the eccentric rod should be disconnected and after drawing 
up the strap bolts it should be tested by giving the strap a half 
revolution about the eccentric. If it is found that the friction 
between the strap and eccentric is sufficient to support the weight 
of the rod, the bolts should be loosened until the strap moves 
freely without lost motion. The double nuts should then be 
' locked and the cotter-pins replaced in the ends of the bolts. 

How to alter engine speed* — The governor used on all Har- 
risburg Engines is the Centrally Balanced Centrifugal Inertia 
Type. A few words of explanation may be of service to oper- 
ating engineers. 

The weight arms are constructed with differential weight 
pockets, to allow of a considerable range of speed adjustment 
without altering the tension of the springs. If an increase in 
speed is desired, remove weights of an equal thickness from the 
weight pockets of the levers, and add weights of an equal thick- 
ness to obtain a decrease in speed. If an increased speed 
causes the governor to " race " or " weave," move the clamp in 
the slot, to which the outer end of the spring is attached, farther 
from the small end of the weight lever. If this does not entirely 
correct this sensitive condition, screw the plug into the spring 
until the racing ceases. If the decrease of speed so obtained 
renders the governor too sluggish in action, move the clamp in the 



HANDBOOK ON ENGINEERING. 281 

slot in the opposite direction. If this does not improve the regu- 
lation, and the speed is lower than desired, add weights of an 
even thickness, increasing the spring tension until the proper 
speed is obtained. The main lever bearings which are equipped 
with anti-friction steel rollers, should be oiled about once a week, 
and taken out and cleaned about once a month ; the other joints 
fitted with compression grease cups, should be treated in the same 
manner. About once a month, also, the springs should be dis- 
connected and the governor and valve gear tested by hand, to make 
sure all joints are working freely. 

The foregoing will apply also to the Harrisburg Standard and 
Ideal Compound Engines, and, in general, to the Harrisburg Self- 
Oiling Four Valve Engines. Adjustment for wear in the valve 
gear connection of the latter type of engines is obtained by filing 
the halves of the bronze boxes on the ends of the rods connecting 
the valves with the wrist plates and rocker arms, and on the 
wrist plate and rocker arm pins, by means of bronze shoes let 
into the sides of the bearings, the wear being followed up by the 
screws provided with lock-nuts, and all bearings lubricated by 
means of compression grease cups. The Harrisburg Corliss En- 
gines, of the larger sizes, are provided with quarter boxes in the 
main bearings with wedge and screw adjustment, and are built self- 
oiling or otherwise, according to size. The lubrication of theprin- 
cipal bearings is accomplished by means of oil cups, and the valve- 
gear connections by means of conveniently arranged grease cups- 

Mcintosh and seyhour high speed engine. 

How to set the valve* — When the engine is sent out from 
the shop, the valves are set and trammed with three inch tram 
from the valve-rod to the valve-rod slide at C Z>, and from the 
eccentric rod to the eccentric rod head at E F, on the valve-slide 
end, and a tram is furnished with the engine, or a new tram can 
be made with exactly three inches distance between the points, 
which will suffice. 



282 



HANDBOOK ON ENGINEERING. 



In case the tram marks become lost, or, owing to wear of 
the valve gear, the length of connection is altered, the proper 
procedure is to put the engine on one center, and then on the 




A Sectional Cut of Mcintosh and Seymour High-Speed Engine, 
Showing Valve and Governor. 

other, and observe the leads which occur when the governor is in 
the normal position of rest, as shown. The lead on the crank end 
should be three times as much as the lead on the head end, if the 
connection between the valve and eccentric is of proper length. 

When the valve is set this way, the cut-off on the two ends 
of the cylinder will be approximately equal at one-quarter cut-off 
on the smaller size engines having inside governors. 

Preliminary to adjusting connections between the valve and 
eccentric, care should be taken that the mark on eccentric G H, 
corresponds to the mark on the pendulum. 

In examining" the steam leads, as described above, it should 
be noted that the surface B on the valve has nothing to do with 
the steam distribution, but it is merely to give ample wearing sur- 
face, and that the steam is admitted to the cylinder through the 
port which is between B and the steam edge which is at A, and 
the lead should be measured between this steam edge and the 



HANDBOOK ON ENGINEERING. 283 

edge of the port leading to the cylinder. On engines of larger 
size having outside governors, a similar method should be em- 
ployed in setting the valves, except that the trams are four inches 
from point to point, and should be used between the valve-rod 
slide and valve-rod, and the eccentric rod and the eccentric 
rod head at governor end, instead of slide end, as above. 

9 

INSTRUCTIONS FOR STARTING AND OPERATING IDEAL 
ENGINES. 

Before starting engine* — Open cylinder cocks and throttle 
valves sufficiently to warm the cylinder and valve. Place sufficient 
oil in the basin under the crank so it will stand one inch above the 
bottom of crank discs. When receiving a new engine from the 
shops with visible stuffing-box and water drain, before you fill 
the crank case with oil, previous to starting, pour water in opening 



Fig, 1. 

in frame into pocket under piston rod stuffing-box, until water 
overflows through trap connected therewith attached to outside of 
frame. Fill cylinder lubricator and start it to feeding. Fill oil 



284 HANDBOOK ON ENGINEERING. 

pump, and pour engine oil into pocket on main bearings. Fill 
eccentric oiler and start it feeding. After the steam chest and 
cylinder are warm, turn the engine over by hand to see that all is 
free and right to start. 

Open the throttle valve gradually, start engine slowly. After 
the engine is up to speed, pump five or six strokes of oil into 
cylinder with oil pump. The oil should flow in streams through 
both pipes on the crank cover into the pockets of the main shaft 
bearings. 

This oil passes from the main bearings through the crank pin 
and is distributed over cross-head pin and slides. Occasionally 
clean out the oil passages in crank pin. 

Supply ♦ as needed, a little fresh oil to the basin, and if the 
oil in the engine bed becomes thick, gritty or dirty, so as not to 
flow freely through oil passages, draw it off and replace with fresh 
oil. Filter the old oil and use it over continuously. Use a pure 
mineral oil that will not thicken by the churning it receives. 

Serious damage and cutting of the cylinder and valve will 
result from allowing the lubricator to cease feeding, even for a 
few minutes. If your engine is a new one from the shops, feed 
plenty of oil through the lubricator and oil pump for the first 
few weeks after starting. Use one drop of oil per minute for each 
ten horse-power, or ten drops per minute for 100- horse-power 
engine, for the first thirty days ; after which, one-half this amount 
will be sufficient, if the oil is of good quality. If your boiler is 
priming or foaming, use double the quantity of oil to protect the 
cylinder and piston from cutting. A little graphite fed into 
cylinder is very beneficial. 

The governor* — Fill the cups on governor bearing with grease 
and give the cap J turn every day. Screw the cap to the stuffing- 
box on dash pot loosely, only using your hand to turn the cap. 
The governor should be taken apart every two or three months 
and bearings cleaned with coal oil to remove gum. If governor 



HANDBOOK ON ENGINEERING. 285 

has a dash pot, it should be refilled with glycerine once or twice 
a year. Oil may be used in the dash pot in place of glycerine, 
unless the engine is in a cold room where the oil is liable to 
congeal. To refill dash pot, unscrew cover on end. 

In taking- the governor apart, allow the sliding block which 
holds the end of the governor spring to remain with its outer edge 
on a line with a mark across the face of the slide, and in re- 
adjusting the spring, place the same tension on it as before, 
which can be ascertained by measuring the length of the thread 
through the nuts before slacking up the spring. If you have 
trouble with springs breaking it is because you are working 
them under too much tension. The speed of the governor is 
changed by moving the weight on the lever. 

To increase the speed of the engine, move the weight on the 
governor lever near to the fulcrum pin. To reduce the speed, 
move the weight out toward the end of the lever. Tightening the 
spring will also increase the speed, but will cause the engine to 
" race," unless at the same time the block which holds the end of 
the spring, is moved toward the center of the wheel. The proper 
way to change the speed is by moving the weight, allowing the 
spring to remain in its marked position. 

Moving- the block, which holds the spring, towards the rim of 
the wheel, will make the governor more sensitive and regulate 
more closely ; but if moved too far, this will cause the governor 
to " race." Moving the block towards the hub of the wheel has 
a tendency to stop the " racing," but if moved too far the speed 
of the engine will be reduced with the increased load. If any of 
the bearings of the governor bind, or require oiling or cleaning, 
the governor will " race." These bearings should be kept clean 
and in good condition and the stuffing-box to the dash pot must 
not be screwed up tight, as that will cause the governor to " race " 
when set for close regulation. 

The face of the slide is marked with a line where the outer 



28b HANDBOOK ON ENGINEERING. 

edge of block which holds the spring should be. Figures stamped 
on the face of the slide, give length of end of eye-bolt extending 
through nuts. This gives the right tension to the spring. 
Tightening the spring will give closer regulation, but will cause 
the governor to " race " if the spring is too tight. " Racing " 
caused by over-tension of spring, can be stopped by moving block 
nearer to center of wheel. 

To set valve. — Should you wish to ascertain if the steam 
valve is properly set, proceed as follows : Take off the cover or 
elbow on outer end of steam chest, so you can have access to end 
of valve. Turn the engine over until the valve has traveled as 
far as it will go towards end of steam chest. Then measure from 
the end of steam chest to the end of the valve, and this distance 
should be represented by the figures in inches and fractions 
on end of steam chest. If measurements do not agree, set valve 
by screwing the valve stem at the ball joint. 

Square, braided flax packing is the best kind for piston rod and 
valve stem. Don't screw the glands up tight ; allow them to leak 
a little. The valve stem has only exhaust steam — don't pack it 
tight. Screw it up by hand only. Screwing the piston rod gland 
up tight may cause the piston to thump or pound the cylinder, 
and heat and cut the piston rod. 

Safety caps. — The safety caps attached to drip valve under 
the cylinder are intended to break, in order to save damage to the 
engine if water enters cylinder. They will protect the engine 
from breaking if the amount of water is not too large to pass 
through the valves and pipes. If they break, they have accom- 
plished their purpose and new ones should be attached. 

Eccentric* — Take up lost motion by reducing the brass liners 
between the lugs on eccentric strap, and unscrew and dis- 
connect the ball joint on the eccentric rod to see that the eccen- 
tric strap will turn freely on the eccentric. If a close fit it will 
heat, cut, seize and break the eccentric rod or valve stem. Allow 



HANDBOOK ON ENGINEERING. 287 

the eccentric strap to run loose ; no harm if it knocks a little. 
It will not wear out of round on account of running loose ; it is 
dangerous to run with the strap snug. 

Ball joint. — Take up lost motion in the ball joint, on the valve 
stem, by unscrewing the joint at eccentric rod and turning or 
filing off the face of the brass part attached to the valve stem, 
so as to allow the male part to screw in a greater distance. 

Connecting-rod* — Take up the lost motion on the crank pin 
bearing by removing the cap and taking out two of the steel 
liners ; take one from each side, put the cap back and set the 
nuts up snug. Disconnect the cross-head end of the rod by re- 
moving cross-head pin, and try lifting the rod up and down to 
see that it does not pinch the crank pin. If it pinches the pin 
when the bolts are drawn up snug, place the liners back or substitute 
thinner ones. Always screw the cap back solid on the liners, and 
keep in sufficient liners so the cap will not pinch the pin when the 
bolts are screwed down snug. Never run the engine without 

HAVING THE CAP SCREWED UP SOLID AGAINST THE ROD, with 

liners between if needed, to make the proper fit. If you remove 
some of the liners be sure to take out an equal amount from each 
side, for if you take out more on one side you are liable to throw 
the cap at an angle in tightening up the bolts, which, in time, 
will cause the bolt to break and is liable to wreck the engine. 

The brass in the cross-head end of the connecting rod is set up 
by a wedge. This wedge is drawn down by the steel bolt until 
the brass is forced solid against the shoulders in the end of the 
connecting rod, which prevents any movement of the brass. 
The upper bolt is used to lock the wedge in position ; also in 
withdrawing the wedge when the brass is to be removed. 

To take up lost motion in the cross-head end of the connecting 
rod, remove the brass and file an equal amount, even and square, 
from each edge of the brass, so as to allow the brass part to come 
up to the pin. When filing the brass, try the pin in the rod 



288 HANDBOOK ON ENGINEERING. 

and do not file enough to allow the brass to pinch the pin when 
the wedge is screwed down solid. If, by mistake, too much is 
filed off, put in a sheet of copper or sheet brass liner, so the 
wedge may be drawn snug without pinching the pin. 

Cross-head. — For adjusting the lower cross-head slide, take 
out the cross-pin, turn cross-head J round with the lower 
brass slipper opposite opening in engine frame ; loosen nuts and 
insert paper or thin metal strips between cross-head and slipper. 
The top slide will never require adjustment. The lower slide 
should run five years before requiring lining or adjustment. 
Turn the cross-head pin J way around every three months. This 
will prevent it wearing out of round. 

Main bearings* — To take up lost motion in the main shaft 
bearings, remove the cap and file, scrape or plane an equal 
amount from each of the babbitt metal liners or strips which are in 
the main bearings under the inside edge of the cap. Remove the 
metal evenly, so the liners will remain of equal thickness at each 
end. Do not remove enough from the liners to allow the cap to 
pinch the shaft when the nuts are screwed down snug. If, by 
mistake, too much metal is removed, put in paper strips on top of 
the liners so the cap can be screwed down solid without pinching 
the shaft. You can tell when the cap pinches the shaft by turn- 
ing the engine over by hand ; it will not turn freely when the cap 
is too tight. With proper care the main bearings will run two 
years before requiring adjustment. None of the bearings of 

THE ENGINE SHOULD BE SO TIGHT AS TO PREVENT TURNING THE 

engine freely over by hand. Always test the engine in this 
manner after adjusting bearings. 

If a bearing heats, stop the engine immediately, take out shaft 
or box, clean out the cuttings, scrape smooth, clean out oil pass- 
ages and run bearings loose. 

Heating or cutting mill never occur if liners are put in so caps 
cannot be set up to pinch the bearings and they receive proper 



HANDBOOK ON ENGINEERING. 



289 



lubrication with oil free from grit or dirt. After adjusting any 
of the bearings, ran the engine for a few minutes ; then stop the 
engine and feel the bearings which have been adjusted to see if 
they are running cool. This precaution may obviate having to 
shut down your engine while performing regular duty. 

Do not allow your engine to run with bearings so loose as to 
thump or pound, as this will cause the bearings to wear out of 
round. If the shaft or wheels run out of true or wabble, it is 
because the main bearings are loose and should be taken up. 
The engine will run smooth and noiseless if bearings are properly 
adjusted. 

THE STEAfl CHEST. 

Fig* 2 shows a section through cylinder and valve. The steam 
chest is bored out and fitted with a pair o r cylinders or bushings, 




Fia:. 2. 



which have supporting bars across the ports, to prevent any pos- 
sibility of the valve catching upon the ports. 

The valve is of the hollow piston type — a hollow tube with a 
piston at each end. The live steam is entirely upon the outside 

19 



290 HANDBOOK ON ENGINEERING. 

of this piston, pressing equally on each end ; the exhaust steam is 
entirely on the inside of the piston, so the valve is perfectly bai- 





Fig. 3 is a Tandem Compound. 

anced and can easily be moved by hand when under full boiler 
pressure. 

Fig* 4 is a cross-section of cylinder and valve of the Tandem 
Compound engine. The cylinders of the Ideal Compound engine 
in Fig. 4, the stuffing-box between the two cylinders, is dispensed 
with entirely. It is replaced by a long sleeve of anti-friction 
metal. This sleeve is light and free to adjust itself central with 
the rod. Grooves are turned on the inner surface, so as to form 
a water packing. 

Both valves of engine are controlled by the same governor on 
the same stem, moving together and varying in stroke as the load 
and steam pressure vary. This gives the advantage of automatic 
cut-off in both cylinders and dispenses with the complication of 
double eccentrics, rock arms, slides and stuffing-boxes. 

The high-pressure cylinder has a piston valve, same as used in 
ail ideal engines. For the low-pressure valve in order to bring it 



HANDBOOK ON ENGINEERING 



291 



into line with the high-pressure valve and keep clearance spaces 
at minimum, which thus gives a quick and wide opening at the 
beginning of the stroke, in order to reduce the pressure on 
exhaust end of high-pressure piston. 




Fig. 4. 

The cover of this valve is held in place by springs and will 
lift and prevent excessive pressure in the cylinder from water or 
other causes. 



FOR INDICATING IDEAL ENGINES. 

The illustration (page 292) shows the reducing motion at- 
tached to engine ready for taking indicator cards. 

To apply the Ideal Indicator Rig: Screw slotted stud in 
cross-head pin, first removing the cap screw. Set the slot per- 
pendicular to line of motion of cross-head. Set cross-head 
exactly in center of its travel. Fasten on top of bed where oil 
funnel is placed, first removing the oil funnel. 

Lever should be adjusted so it will travel in slot without strik- 



292 



HANDBOOK ON ENGINEERING. 



ing bottom, or passing out at top. Make sure that lever will 
travel freely in slot without binding. Select a hole on string 
carrier that will give the necessary motion to indicator drum. 





^ Biw ^ 1 








^--, '^ :;.- ~ :/ -'%^WM> ;^ 


~: '"^mmr\ 






'■ ; ~ ■ ^ :■ 


, 






'mMVM 








--.-■■>, T^rnm^- 





Fig. 5. 






With string attached from indicator through hole, so adjust this 
carrier that lines drawn on polished surface shall come exactly 
parallel with string. Make all adjustments while cross-head is 
in center of its travel. 



POINTS ON STARTING AND RUNNING A WESTINGHOUSE 
COMPOUND ENGINE. 

In the compound engine, the automatic governor is located 
on the shaft inside an inclosed case filled with oil, which forms 
the center of one band wheel. Its action varies the travel of 
the valve in accordance with the amount of work demanded of 
the engine. The other end of the shaft carries an ordinary 
band-wheel, or combination pulley, of any required diameter and 



HANDBOOK ON ENGINEERING 



293 



face. Set up the engine as directed, keeping the combination 
pulley, or band-wheel, as close to the engine as possible. Work 
the wheel on by turning it around while the shaft is held station- 
ary. Do not attempt to drive it on. 




The above is a cut of the Westinghouse Compound Engine*. 

In order to put on the governor case with its band- wheel, it will 
be necessary to first remove the lid or cover of the case, so as to 
get at the set screws and key way. It is to be put on carefully 
and should not be driven on hard enough to in any way injure the 
shaft. The keys are to be carefully fitted to their places, and 
this should be done by a competent mechanic. It is not pos- 
sible, in every case, for the wheels to be put on the engine to 



294 HANDBOOK ON ENGINEERING. 

which they belong and keys fitted in their proper places, for 
various reasons ; therefore, the keys are left as they come from 
the planer, a trifle full of the required size, so that a little iiling 
will bring them to a good fit. If the keys are not fitted in well 
and carefully at the start, they may become the cause of a great 
deal of subsequent trouble ; but if this be well done at the 
beginning, there will be no trouble afterwards. It is the practice 
of some to tie a tag to each key, designating which one is intended 
for the governor case wheel and for the band wheel. It is im- 
portant they should not be put in the wrong places. If the band 
wheel key should be a trifle too long, no harm will result ; but if 
the governor case key be too long, it will protrude through the 
case and bind the eccentric so, that the latter will not have free 
movement across the shaft, and this will seriously attract the 
regulation of the engine. The key in the governor case should 
be from J" to J" shorter than the hub in the governor case, to 
prevent this possibility. When the keys are well fitted they should 
be driven home with a degree of tightness depending on the size of 
the engine, and the set screws should be pulled down hard and 
fast to hold them. The keys are not intended to fit top and 
bottom, but must fit exactly sideways. 

After the governor case with its wheel is properly located on 
the shaft, the key fitted and set screws pulled down hard and fast, 
the governor case lid is to be put on, having a paper gasket, both 
on its outer edge and at the hub, to prevent leakage of oil past 
these surfaces ; and it is to be bolted up tightly in its place, and 
the governor case completely filled with cylinder or Dalzell crank- 
case oil, through a connection provided for this purpose. 

Turn the engine over by hand to make sure that everything is 
free. Before starting the engine for the first time, oil both pistons 
thoroughly by taking off the relief valves and pouring oil into the 
ports. This oil will work through the valve and oil it also. 
Swing aside the bonnets from the crank case, and see that the 



HANDBOOK ON ENGINEERING. 295 

latter is clean and free from the cinders and dust of travel, which 
generally find their way into the interior. When found to be per- 
fectly clean, supply oil and water according to the following 
directions: Pour in water until it makes its appearance at the 
outlet of the overflow cup ; then pour in one gallon of Westinghouse 
crank-case oil for every 10 H. P. of the rating of the engine for 
the smaller compounds, and about half this amount for the larger 
ones. This will raise the water and oil in the interior to such a 
level as to almost touch the crank-shaft, so that the connecting 
rods will be plunged into the liquid at every revolution. Takeoff 
the eccentric strap ; clean it thoroughly, also clean the hollow 
eccentric rod, then oil and replace it. Be liberal in the use of oil 
all over the engine, at least for the first few days. Remember 
that there are two large cylinders and a valve to be lubricated and 
that the low-pressure cylinder gets its oil only through the high-pres- 
sure cylinder. The engine should now be ready to start. Fill 
the automatic lubricator on the steam pipe with good cylinder 
oil ; fill the side oil cups over the main bearing with Westing- 
house crank-case oil, and open the drip-cocks over each main 
bearing, so that the drip is continuous and regular at the rate of 
about 2 to 10 drops per minute from each cup, according to the 
size of the engine. If undue service is required of the engine, so 
that the main bearings show signs of heating, the amount should 
be increased. Start the automatic lubricator ; give the eccentric 
strap some direct lubrication from a squirt can, and start the cup 
over the rocker arm to feeding from each cock. 

To start the engine* — the throttle valve being closed, open 
the drain cocks in the throttle-valve and steam and exhaust pipes, 
blow them out thoroughly and then close them. Open both cylin- 
der drain cocks ; raise the check valve on the crank case by set- 
ting the handle down ; open the by-pass valve. Turn the engine 
round until the high-pressure piston is on the upper center. Now, 
open the throttle-valve slightly, for the purpose of warming up th*> 



296 HANDBOOK ON ENGINEERING. 

steam-chest and valve equally, as otherwise the valve, by heating- 
quickest, may expand and bind. The engine being on its center 
will not start. When sufficiently warmed up, say in three minutes 
by your watch, close the throttle value for an instant and bar the 
engine off the center. Then open the throttle- valve quickly, but 
not too far, which will insure the engine passing the first center. 
As soon as the engine is up to speed, close the by-pass valve 
tight and keep it closed thereafter. When the water is thor- 
oughly worked out of both cylinders, close the cylinder cocks 
and keep them closed, and at the same time, close the check valve 
and open main throttle-valve gradually until it is wide open. 
Never attempt to regulate the speed of the engine by the throttle- | 
valve. 

In stopping the engine, open the cylinder cocks, check valves 
and by-pass valve and close the throttle slowly, so as to allow the 
engine to lose speed by degrees. Do not stop suddenly, as the 
momentum of the pistons and fly-wheels, at standard speed, is 
great, and the strain thrown on the connecting rods and crank- 
shaft, in being suddenly stopped, is unnecessary and may, in time, 
become injurious. 

In general, it is well to run a new engine empty (that is with 
no belts on) in order to be certain that everything is right ; then, 
if the performance is all right, the belts can be thrown on. 

With a compound engine properly adapted to its work, not 
overloaded, and running under proper conditions, the duty of the 
engineer may be said to be merely nominal. Nevertheless, this 
engine, when it requires the attention of an engineer, needs the 
proper kind of attention. One competent man can operate a 
very large number of these engines. What is meant in this con- 
nection by the terms ' ' properly adapted ' ' and ' ' proper condi- 
tions," is: a load corresponding to a mean effective pressure in 
the high-pressure cylinder not exceeding one-half of the boiler 
pressure ; a boiler pressure as high as possible, the engine erected 



HANDBOOK ON ENGINEERING. 



297 



in compliance with the directions given, and the directions as to 
lubrication followed carefully . 

The wear is constant in one direction, namely, downward. 
The steam acts only on the upper side of the pistons. The two 
crank-pins are exactly opposite each other. Each piston in its 
downward stroke raises the other piston. The direction of the 
wear on all the bearings being downward, the lost motion may be 
considerable without detriment to the quiet running of the engine. • 
In starting and stopping the engine, however, the accumulated 
lost motion will cause a noise, inasmuch as this motion is taken 
up at each revolution ; the greater the amount of lost motion, the 
greater this noise will be in starting and stopping. The cause of 
this is apparent; the crank, while the engine is stopping, must 
pull the piston down and the effect of lost motion then becomes 
similar to that in a double-acting engine. The effect of this 
action is not conducive to good wear or long service. It allows 
a shock to come on the connecting rod strap with con- 
siderable force ; this wear, therefore, should be taken up fre- 
quently, but it can be allowed to accumulate to a greater 
degree than will be possible in any double-acting engine. 
The wear is taken up on both ends of the connecting rod at once, 
by the "upper bolt at the lower end. The engineer on opening 
the crank case will see a bolt with a squared end and a lock nut ; 
with the large end of the socket-wrench, he will slack off the lock 
nut, and then with the small end of the wrench he will turn the 
bolt to the left until the brasses come up solid ; then slack off 
half a turn and set up the lock nut. The construction of the rod 
and the way in which a single wedge is made to take up both 
ends of the rod at once, is evident from the cut. The piston 
wrist-pins, if worn or cut, should never be dressed off or turned 
down, as they will not fit the bushing or have a proper bearing. 
Order a new pair, and throw the old ones away. When the 
babbitt is about worn out of the main bearing shells, they can be 



298 HANDBOOK ON ENGINEERING. 

re-babbitted and pat back again. The cylinder packing- rings 
will, after much wear, become unfit for service, and will allow 
steam to blow past the pistons into the crank-chamber. There 
will be at all times, when the engine is running loaded, a small 
amount of vapor arising in the crank-case. This does not 
necessarily indicate that there is a leakage of steam past the 
pistons, as the heat generated by the splashing of the water on 
the hot pistons and cylinders, and by the leakage of the hot 
water of condensation past the pistons, will heat up the water 
contained in the crank-case, until it vaporizes slightly. New 
packing rings can be easily sprung into place by the engineer. 

The principal duties of the engineer will be to see that the 
automatic lubricator, which oils the cylinders and valve and the oil 
cup over the rocker arm, perform their work properly and regu- 
larly. Feed slowly, drop by drop, according to the requirements 
of the engine. The engineer must also see that the oil tanks on 
the sides of the engine are supplied with oil and fed slowly, drop 
by drop, into each main bearing. 

The inclosed construction of the engine, whereby all oil used 
in lubrication is completely distributed on the wearing surfaces 
and is prevented from wasting, renders it unnecessary for the 
engineer to pay as close attention to this engine as to any other, 
as it, in a sense, lubricates itself. The crank-case bonnets should 
be removed regularly, preferably every morning, as it is the work 
of only a few minutes. The interior of the engine should be 
examined to make sure that no nuts or bolts (of which there are 
the fewest possible number) have worked loose, bushings worn 
out, or lost motion become unduly great ; this internal examination 
is absolutely imperative, at least, once a week. The proper 
drainage of water in the steam pipes should demand his attention, 
to prevent any entrainment, resulting from the foaming of the 
boilers or from any other cause. Entrained water is always a 
prolific source of trouble in steam engineering ; it is particularly 



HANDBOOK ON ENGINEERING. 



299 



troublesome in all piston valve engines, even with Westinghouse 
engines, . which are provided with water relief valves. The 
engineer should become thoroughly acquainted with his engine so 
as to understand its operation and principle, and be at all times 
familiar with its precise condition. All adjustments being made 
in the shop before shipment, it is unnecessary for the engineer to 
set any valves or take any part in the adjustment of a new engine ; 
but as wear occurs, he must be able to intelligently make the 
needful adjustments of wearing parts. After an engine has run 
a long time, the downward wearing of the reciprocating parts will 
have the effect of throwing the valve slightly out of adjustment. 
That is to say, it will draw the valve gear downward with the 
shaft, and favor one cylinder more than the other. The valve, 
therefore, will require resetting occasionally, but not at all fre- 
quently. It should be adjusted by lengthening the eccentric rod, 
just the amount to which the shaft is worn downwards. 




MAIN BEARING. 



MAIN BEARING. 



The main shaft bearings are now made adjustable. There is 
a slight difference of construction here in the various sizes, 
occasioned by limited space in the castings ; but they are all 
alike in this respect, that the bottom 'half of the main bearing is 
stationary, being turned off on its outer shell eccentric with the 
shaft journal and held down firmly by a long set screw on each 



300 HANDBOOK ON ENGINEERING. 

side, which prevents it from rotating or from rattling loose. The 
top half of the main bearing is adjustable downwards, so as to 
follow up any wear either of the babbitted bearing or of the shaft. 
In the 8 and 13x8 and 9 and 15x9 engines, this top half of 
main bearing is adjusted downwards by three set screws located 
at the apexes of a triangle, and the bearing is locked firmly by 
three tap bolts oppositely placed so as to hold it secure after 
adjustment, In the case of all larger sizes of compound en- 
gines, the downward adjustment is made by wedges bearing on 
the inclined tops of the upper half of the bearing. These wedges 
are moved and locked by a tap bolt in each end, which passes 
through and draws against the shell of the crank-case head. The 
top half "of main bearing is drawn up and locked in position after 
adjustment by tap bolts which pass down through the top shell 
and are screwed into the bearing. Some of these bolts and wedge 
screws are inside of the crank-case, and adjustment must, there- 
fore, be made while the engine is standing idle. It is customary 
to mark with an arrow head on the outside of the crank-case head 
to indicate which way the wedge will move to tighten up. 

The proper condition of the compound engine, while perform- 
ing its work, is one of perfect quiet, without leaks of steam past 
any joint and without noise. Any noise in the engine, after it 
has attained full speed, may be immediately accepted as an indi- 
cation that something is wrong and the engineer should familiar- 
ize himself with it, so as to be able to discover the cause and the 
remedy. Hot bearings may be said to be unknown in this 
engine ; occasionally, however, they have been met with but they 
are always traceable to the use of improper oiL; dirt and grit in 
the oil; the filling up of oil grooves, or the wearing out of the 
oil grooves in the main bearing shells ; or to worn out or broken 
packing rings in the piston. The eccentric strap is the only point 
liable to run dry, and the engineer should see that the oil cup 
feeds with certainty. All joints in the governor are bushed and 



HANDBOOK ON ENGINEERING. 301 

these bushings are provided with sufficient oil holes ; they can 
readily be replaced with new ones when necessary. In replacing 
bushings, always be careful to provide ample oil-holes, the same 
as were in the old removed bushings, and observe the same pre- 
caution in the case of other repairs. 

As above stated, it is the duty of an engineer to know in what 
condition every part of his engine is at all times. All wearing- 
parts should be examined from time to time, so they can be re- 
placed before they are entirely worn out and damage is done. It 
is too late to find out that a bushing needs replacing after it has 
been worn entirely through and the pin has cut into the solid 
metal. While the engine is built of the very best materials and 
with the greatest care, and while the means and the opportunity 
for lubrication are the best known, yet it is not claimed that 
it possesses any miraculous virtues by which it will run on for- 
ever without any attention and without repairs. Nowhere is 
the old proverb more forcibly demonstrated than in the case of 
machinery, that '-' A stitch in time saves nine." The wearing 
parts of the engine are few, are easily reached and placed, 
and the engineer who waits until same accident happens to 
announce that he has long neglected the proper inspection of 
the part which could, at the proper time, have been replaced at 
a trifling cost, is not worthy of being placed in charge of any 
machine more complicated than a wheel-barrow. The same 
principle will apply with equal force to machinery of every type. 
There is a proper time to replace worn parts and a time it is too 
late to replace them. 

HOW TO SET THE MAIN VALVE. 

The only exact and final setting of the valve is by means of 
the indicator. As the valves are permanently set and all adjust- 
ments made before the engine is shipped, it is not supposed that 



302 



HANDBOOK ON ENGINEERING. 



the engineer will have occasion to reset them. Should the neces- 
sity for setting the valves arise, however, the following method 
will be sufficiently accurate : Break joints and take off the throttle- 
valve. The steam ports in the bushing will then be seen through 
the steam connection S. (This opening is on the side in fact, but 
is here shown on the top for convenience.) Bring the high- 
pressure piston exactly to the top of its stroke by turning the 
shaft in the direction the engine runs. This may be ascertained 




by either taking off the water relief valve and measuring through 
its port, or more conveniently, by bringing the middle of the key- 
way in the shaft exactly over the center of the shaft. The key- 
ways are planed exactly with the cranks, so that the position of 
the key way is the position of the high-pressure piston. With 
this piston at the top of its stroke, the valve edge a «, should 
show about T ^ of an inch port or lead, and be moving towards 
the right as you stand behind the engine. If out, it may be 
brought to position by screwing the valve-stem into or out of the 
valve which is tapped to receive it. Be sure and set the jam nut 
solid when through. 



HANDBOOK ON ENGINEERING. 



303 



After a test of a compound engine has been completed with 
the indicator, and the valve has in this manner been accurately 
adjusted, marks are scored on the end of the rocker arm, at its 
junction with its supporting bracket, in order to show the extreme 
points of oscillation of the rocker arm. If, therefore, in starting 
up a new compound engine, the eccentric rod is too long or too 
short, these marks will not coincide when the engine is turned 
round by hand to examine this point. The eccentric rod must 
then be adjusted with the nuts provided for that purpose, until 
the scored lines on the rocker arm will coincide exactly. When 
this rod has thus been proven correct, the engine should then be 
put by hand on the dead center, with the high-pressure piston at 
the top of its stroke. In order to prove this upright position of 
the high-pressure piston exactly, two lines are scored on the 
faced-off end of the crank-box head on the high-pressure side, to 
which marks the keyway in the main shaft must be brought 
exactly. Then remove the back head from the steam chest and 
measure the distance from the rear end of main valve to the end of 
the steam chest, while the engine is in this position. This 
distance measured will be found stamped with steel figures on 
the finished face of the steam chest, underneath the back head. 
If the valve has not been disturbed, the measurement thus taken 
will agree with the figures. If it has been disturbed, the valve 
must be adjusted to correspond with the measurement. 

ADJUSTMENT OF ECCENTRIC STRAP AND CONNECTING ROD. 

Before starting the engine for the first time, the eccentric strap 
must be taken off and both the strap and eccentric carefully 
cleaned and lubricated with clean oil. The eccentric rod is 
hollow and might contain dirt or other injurious matter, and 
should be examined and thoroughly cleaned before putting on the 
engine. There must be a sufficient number of liners between the 



304 HANDBOOK ON ENGINEERING. 

joints of the strap, so that when the bolt is pulled up hard and 
tight the eccentric strap will still be free to run without binding. 
After the bolt has been tightened, take hold of the strap and 
shake it back and forth to be sure that it is free. If it binds in 
the least, it is certain to heat or cut either itself or the eccentric 
or probably both. When the upper ball joint on eccentric rod 
becomes worn it should be adjusted to take up the lost motion 
promptly. 

As to the connecting rods, the lost motion should be simply 
taken up without binding. No possible good, but much harm, 
can come from too tight an adjustment, 

GENERAL INSTRUCTIONS FOR HOHE REPAIRING. 

How to put in new bushings and cut the oil holes and 
grooves* — When new bushings are shipped to fill repair orders, 
they are turned to gauge so as to fit tightly in their respective 
places. A very careful mechanic may, by the use of a wooden 
block and hammer, be able to drive in bushings properly. The 
much safer course, however, is to use a bolt which passes through 
the bushing, and a nut and washer ; by screwing up the nut and 
taking reasonable care, the bushing is thus drawn surely and 
gradually into place. After the bushing is in place, the oil 
grooves must then be cut into it with a half-round chisel and 
hammer. The oil-holes must then be drilled ; these latter should 
be large and free ; no harm can come from having them too large, 
but much trouble will result if they are too small. The oil should 
have very free access through these holes to the grooves. We 
have conducted a long series of experiments to determine what 
form or style of oil groove would produce the best lubrication, 
and consequent^, the most satisfactory results in each bushing, 
and, therefore, urge that grooves be cut in new bushings in strict 
accordance with the grooves and oil holes as shown in the old 



HANDBOOK ON ENGINEERING. 305 

fmshing which has been removed. This course is safer and bet- 
ter than to try experiments of your own. 

' How to rebabbitt connecting: rods* — Connecting rods may be 
Ire-babbitted at home, if preferred. You should provide yourself 
with a plug, preferably of cast-iron, turned to the exact diameter 
of the shaft or crank-pin and squared accurately on the end. A 
perfectly true surface is then required on which to lay the rod, so 
that the plug will stand in its proper position, exactly square with 
the rod. The original length of the rod must be known, and will 
be furnished by us on application, by stating the number of your 
engine. The center of the plug must then be placed at the proper 
distance from the center of the eye of the connecting-rod pin, and 
the babbitt metal poured into place. Moistened fire-clay will be 
found very convenient for confining the molten babbitt metal 
within its proper limits. After cooling, the babbitt metal should 
be dressed with chisel and file. Bear in mind that heavy service 
is required of these connecting rods, and that the engines run at 
higher speeds than is possible in any other type of engine, hence, 
nothing but first-class babbitt metal, or " genuine " babbitt 
metal, as it is called in the trade, will answer the purpose. I 
would, however, advise that the brasses be sent to the shop to 
be re-babbitt, and that duplicates be kept on hand, if necessary. 
How to rebabbitt main bearing shells* — This is a very diffi- 
cult piece of work to do at home, and it is not recommended that 
you attempt it ; it cannot possibly be done accurately by any one 
without special appliances for the purpose. The lines of the bab- 
bitt, internally, when complete, must be exactly parallel with the 
outside lines of the shell, else the shaft cannot lie on its bearings 
with equal contact throughout the length of the shell. The lack 
of equal contact will cause the shaft to bind, and in all probabil- 
ity, the limited bearing surface will cause friction and heating. 
The only way in which main bearing shells can be properly re- 
babbitted at home, is to first provide yourself with what is called 

20 



306 HANDBOOK ON ENGINEERING. 

a "jig," which is simply a special device that holds the main 
bearing shell and the central plug in their relative positions, ex- 
actly, while the babbitt metal is being poured. After cooling, 
the ends of the shell should be dressed and the oil-holes and 
grooves must be properly cut, exactly as they existed when the 
shell was new. A simple and more satisfactory method, would 
be for each owner of an engine to purchase an extra pair of main 
bearing shells ; in this way, while one pair of shells is in use in 
the engine, the other pair may be sent in for rebabbitting, with- 
out the loss of time, and at trifling cost. Use nothing but first- 
class " genuine " babbitt metal in the main bearing shells. 

How to repair worn or badly scored wrist-pins. — Instruc- 
tions on this point are very simple: Don't! If , on examina- 
tion, you find you have allowed the wrist-pins at the upper 
ends of the connecting rods to become worn, or even badly 
scored, it is recommended that, having bought a new pair 
of wrist-pins and rebabbitted the brasses, you immediately take 
out the old pins and throw them away. It is useless to attempt 
to repair worn wrist-pins. If you turn them down until they 
present a smooth exterior (as some have proudly announced they 
have done) the diameter of the pin is so reduced that it will not 
fit the brasses and the reduced bearing surface will soon destroy 
it. Or, if you attempt to use a badly scored wrist-pin in new 
brasses, it will cut them out so rapidly that it would be more 
economical in the end for you to buy new wrist-pins than to 
attempt to use the old ones. The service on the wrist-pin of any 
engine is extremely heavy. These pins are made with the best 
possible care, using the best selected materials, and after machin- 
ing them they are ground in special machinery. The brasses are 
lined with the finest possible babbitt metal and should last a long- 
time under heavy duty if properly lubricated ; yet, the use of an 
improper oil in the crank-case — either volatile or gritty — nul- 
lifies all these precautions. Therefore, if you find on examina- 



HANDBOOK ON ENGINEERING. 



307 



tion, that the wrist-pins in your engine have become badly worn 
or badly scored, I would urge you to throw them away and buy 
new ones. 




Where the inclosed form of governor is used, the governor 
case is to be filled completely full of good cylinder oil, or with 
James Dalzell & Son., Ltd., Crank-case oil. Use nothing else. 
A nipple is screwed into the face of the inner case and extends 
through the first flange of the wheel in a radial direction. This 
nipple is closed by a cap. Turn the engine around till this nipple 
is on top and fill the case entirely full through the opening. The 
joint at the outer rim of the case, also the joint on face of hub, is 
made with a paper gasket. The oil is prevented from escaping 
along the spindle of the eccentric and out past the eccentric by a 
leather packing ring fitting around the spindle and between the 



308 HANDBOOK ON ENGINEERING. 

eccentric and the face of the case. If, after service, this should 
leak oil when the engine stands still, you must pack it tighter by 
putting in a thicker packer-ring of leather, so it shall be held 
tightly in its place and prevent the passage of oil. Be careful in 
locating the governor case on the shaft, so that the average posi- 
tion of the eccentric rod shall be vertical and that its extreme 
positions shall be alike on each side of a vertical line drawn 
through the center of eccentric. Be very careful as to the lubrica- 
tion of the eccentric strap at the start. After it runs for a few 
weeks and gets a good surface, it will require little attention 
beyond regular oiling. When you start the engine, be sure to 
put plenty of oil on the eccentric direct, by hand. 

The best means for lubricating the valve and pistons is an 
Automatic Sight Feed Lubricator, which is treated of elsewhere. 
It is manufactured in a variety of forms, many of which are very 
effective in their working. With a good cylinder oil, the number 
of drops per minute can be regulated so as to effect the greatest 
economy of oil and distribute it in such a way as to do the 
engine the greatest amount of good. Any other system of lubri- 
cating the cylinders is defective. It will not suffice to give the 
engine an hour's supply of oil at one dose and then allow it to run 
without any cylinder lubrication for the remainder of that hour. 
The construction of the Westinghouse engine is such as to be 
favorable to the economy of oil in this direction, because the 
pistons moving up and down in a vertical direction do not have 
the same tendency to wear as in the case of a horizontal engine, 
where the heavy piston-head drags back and forth. These im- 
mense bearing surfaces, moreover, reduce the amount of pres- 
sure per square inch to a minimum. The Automatic Lubri- 
cator is to be attached to the steam-pipe, within easy reach of 
the engineer, so that it can be refilled without loss of time. 
With each lubricator is packed specific directions for starting 
and operating it, which should be followed carefully. It may 



HANDBOOK ON ENGINEERING. 309 

be well to note here that, in order to get the best results 
and avoid trouble, no other than a first-class cylinder oil 
should be used in the cylinders. Approximately, one pint of 
cylinder oil per day for every fifty horse-power, and pro- 
portional, will be required for engines, depending on the amount 
; of work to be done. The lubricator furnished on each engine 
will serve as a partial index of the quantity of oil required. 
These cups are not intended to hold over 8 to 10 hours' supply 
in any case. Feed regularly and slowly. The use of Valvoline, 
or 600 W. Vacuum Cylinder Oil, made by the Vacuum Oil Co., 
Rochester, N. ST., is recommended, although there are others 
who make a first-class article. 

SOME POINTS ON CYLINDER LUBRICATION. 

"In the first place, use the best automatic feed cup that can 
be secured. Don't be satisfied with the old-fashioned direct 
feed, or a cheap automatic. A good cup will save many a hun- 
dred per cent on its cost in a year. Don't get the kind which, on 
account of its peculiarity of feed, is adapted for a light oil only ; 
you will then be shut out from using a dark oil, which may 
be far more serviceable and economical in every respect. Get 
a cup where the drop of oil cuts off square and passes either 
down or up through a glass tube into the steam pipe. This 
kind will feed oil perfectly ; if yours is not this kind, it will 
pay you to change it." 

"Take good care of your cup. Don't let it leak around 
the glass tubes or other joints, for if it does the water will escape 
as it condenses, and the oil will clog up the escape pipe and 
stop feeding. Use in it only the best grades of cylinder oil, 
made by large manufacturers of established reputation. Don't 
ran in your cylinders any kind of poor stuff that may be offered, 
oecause it is cheap ; it is a dangerous experiment. Feed a good 



310 HANDBOOK ON ENGINEERING. 

oil sparingly — don't drench the cylinder. Too much oil is as 
bad as water in the cylinder. Engineers have been known to run 
a couple of quarts per day of cheap oil into an ordinary sized 
cylinder, and thought they were doing just right; this is positive 
abuse of an engine. In almost all cases where too much oil is fed, — 
cut it down. Two to four drops per minute on engines from 50 
to 150 H. P. are all that is necessary, if the oil is good. Just 
enough to do the work and no more, will afford best results. As 
long as the valve stem does not cause trouble, you may know the 
valves are working smoothly and that you are giving oil enough. 

AUTOMATIC LUBRICATORS. 

An Automatic Sight Feed Lubricator should be furnished 
with every engine, which enables the engineer to see the oil as it 
is fed drop by drop to the engine. The construction of these 
lubricators is such that the steam entering a chamber is condensed 
and this water of condensation finds its way into another com- 
partment of the lubricator, wherein is contained the oil to be fed 
to the engine. The drop of water, by reason of its greater spe- 
cific gravity, seeks the bottom of this oil compartment and forces 
out an equivalent bulk of oil into the steam pipe, whence it is 
carried by the current of steam into the cylinders and is distrib- 
uted upon the wearing surfaces intended to be lubricated. This 
method insures regularity and economy. 

There are numerous automatic lubricators made by various 
manufacturers throughout the country, many of which will per- 
form their functions successfully. I have used several of the 
best types, and consider any of them suitable for the purpose ; 
jut herewith is submitted, with description of the cup I have 
been using for some years. 

This is the up-feed cup, showing an external view and sec- 
tional view of the same. Attachment is made to the steam-pipes 



HANDBOOK ON ENGINEERING. 



311 



at the points F and K. In operation, the condensing chamber F 
provides for the condensation of steam which enters at the pipe F. 
This water of condensation passes down through the valve D and 
through the tube P shown in the section and discharges into the 
bottom of the oil vessel A. This vessel is filled with oil when the 
cup is started, the height of oil being shown in the index glass J. 




THE «' DETROIT" LUBRICATOR. 



The operation is as follows : The valve N being opened, the valve 
D is opened and the drop of water is allowed to pass from the 
condensing chamber F downward through the water tube and into 
the bottom of the oil chamber A, where it displaces a drop of oil 
of equal bulk on account of its greater gravity, and this drop of 
oil is forced out past the valve E, making its appearance in the 
feed glass H, as it starts on its way to the steam-pipe. It is 
carried by the current of steam to the engine and lubricates the 
valve and the pistons. When the oil cup is empty, the valve D 



312 



HANDBOOK ON ENGINEERING. 



is closed and the drain valve G is opened, which will allow the 
water in the oil chamber to be blown out preparatory to the re- 
filling at the plug C. By opening the valves G and D, steam will 
be blown through the sight glass ,/, thereby clearing the same 
from any clogging up of the oil, which would disfigure it. The 
amount of oil to be fed by the lubricator will be regulated by the 
valve D, controlling the amount of water admitted, and the valve 
E controlling the discharge of the oil into the sight glass. The 
valve N is to be left wide open in operation and its object is to 
provide for the accidental breaking of the glass II. 




Sketch showing proper method of attaching cup to prevent the 

oil from dropping into the well, and not going into 

the cylinder. 

These cups should be attached to the steam pipe, in strict ac- 
cordance with the instructions contained in the box in which the 
lubricator is packed. The greatest enemy to proper performance 
is leakiness ; all joints must be absolutely tight, otherwise the ! 



HANDBOOK ON ENGINEERING. 313 

water of condensation, instead of performing its duty of displac- 
ing- the oil, will ooze out at the leaks and the cup will refuse to 
work. In most cases, provision is made for a column of water 
which may stand 12" or more in height and enable the cup to 
work more positively, by giving it a greater pressure in the dis- 
placement chamber, due to the height of the column. A suitable 
oil is essential to the proper working of such a lubricator, as well 
as to the proper lubricating of a steam-engine. An improper oil 
will not feed through the cup as it should, on account of its dis- 
position to disintegrate and go off in bubbles, when exposed to 
the heat of the steam. 

SETTING A PLAIN SLIDE VALVE WITH LINK riOTION. 

The setting of a slide valve operated by a link motion does 
not differ materially in principle from the method pursued when 
setting the ordinary slide valve driven by one eccentric. A link 
motion may be considered as a means of driving a valve by two 
independent eccentrics, either of which controls the functions of 
the valve wholly or in part, according to the position of the link. 
Thus when the link is in either extreme position, the eccentric 
driving that end of the link in line with the link-block pin may be 
considered as being entirely in control of the valve action, and, 
vice versa, when the link occupies the other extreme position of 
its throw, as actuated by the reverse lever, the other eccentric 
becomes possessed of the controlling function. Practically, 
however, the operation of the link motion is very complicated and 
the movement of one eccentric materially modifies the action of 
the other. Since the interfering action is least at the extreme 
positions of the link and greatest in mid-gear, the plan is followed 
of setting the valve with the link in full gear both forward and 
backward motion, and, as before stated, the procedure is on the 
theory of independent action of the eccentrics. 



314 



HANDBOOK ON ENGINEERING. 



In the accompanying diagram, a link motion is shown driving 
a plain slide valve without the intervention of a rocker. Each 
eccentric is set with reference to the crank-pin, the same as it 
would be with a simple slide-valve engine. The eccentrical is 
set on the shaft with the same angular advance, QMO, as would 
be required for an ordinal engine to run in the direction indi- 
cated by the arrow. Now, since the crank pin is at C\ if it were 
necessary to reverse the simple engine with one eccentric, it would 
be necessary to change the position of the eccentric so that instead 
of being ahead of the bottom quarter line QM, it would be ahead 




of the top quarter line PM by an amount of angular advance made 
necessary by the lap and lead of the valve. Therefore, the eccen- 
tric would come in the position of the eccentric A 1 , or with its 
center line coinciding with MJSf, giving it the angular advance 
PMN. Now it should be clear that if an engine is to be equipped 
with two eccentrics, so that it may run with equal facility in 
either direction, they will occupy the positions A and A 1 . We 
will suppose that an engine having a link motion is to be over- 
hauled and the valve motion to be properly set. This will mean 
that the eccentrics will be properly located for the correct angular 
advance, and that the eccentric rods will be adjusted to the right 
length. When these conditions are obtained, the valve should 



HANDBOOK ON ENGINEERING. 315 

perform its functions properly in both forward and backward 
motions, and also when the link is " hooked up." 

Before starting" to set the valve, it is best to take a general 
survey of the valve motion parts and see if the eccentrics are 
somewhere near the proper location on the shaft relative to the 
crank-pin. If they are obviously much out of position, they 
should be shifted and adjusted as near the correct position as 
possible by the eye ; doing this at the beginning will often save 
confusion and much time. The dead centers will be found by the 
method given on page 195. The operation should be carefully 
performed, as upon it depends the success of the work. After 
having found the dead centers and having them marked so that no 
mistake will occur when " catching " them with the tram, the 
valve positions may be taken for the four positions , that is, front 
and back centers in forward motion, and the front and back 
centers in backward motion. Put the reverse lever in full gear in 
one motion or the other, whichever is most convenient, and turn 
the fly-wheel in the direction the engine would run for the given 
reverse lever position. Suppose the link stands in the position 
shown in the diagram, the fly-wheel should be turned in the direc- 
tion indicated by the arrow until the dead center is reached, 
which is known when the tram drops into the prick mark. The 
position of the valve is then noted and a measurement taken. If 
the valve shows the steam port open, measure the distance with a 
,steel scale, or it may be done by sharpening a stick wedge-shaped 
and shoving it into the opening. By noting the depth to which 
it goes at the valve face the opening can be readily measured on 
the removal of the wedge. We will suppose the distance is found 
to be J". The measurement should be set on a sheet of paper 
laid out as follows : — 

FORWARD MOTION. BACKWARD MOTION. 

Front center, Front center, 

Back center. Back center, |" lead. 



316 HANDBOOK ON ENGINEERING. 

It will he seen that the valve opening is set down as being 
|" lead, and as being on the back center in the backward motion. 
After having verified the measurement taken, the engine can be 
" turned over " in the same direction as before until the opposite 
dead center is caught by the tram. It may be found that the 
valve does not show open in this position but covers the steam 
port. To find the position of the valve edge relative to the steam 
port, scribe a line in the valve seat face along the edge of the 
valve and then turn the fly-wheel until the valve uncovers the 
steam port. The distance the valve laps over when the crank is 
on this dead center can then be readily measured. Suppose the 
distance is found to be J". It is set clown on the log as 
follows : — 

FORWARD MOTION. BACKWARD MOTION. 

Front center. Front center, |" blind. 

Back center. Back center, |" lead. 

The valve position is put down as being i" blind, which is the 
same as saying that it has J" negative lead, and is fully as com- 
prehensive as the latter term. The reverse lever should now be 
thrown into the opposite gear and the measurements taken for 
both front and back centers the same as has been described for 
the backward motion. It may now be supposed that when all the 
measurements have been taken the log reads as follows : — 

FORWARD MOTION. BACKWARD MOTION. 

Front center, i" blind. Front center, J" blind. 

Back center, T 5 g-" lead. Back center, §" lead. 

When in forward motion, the valve is open T 5 ¥ " on the back 
center and lacks J" of being open when the crank is on the front 
center. The total lead due to the angular position of the 
eccentric is T 5 ¥ " minus J" = T y. One-half the total lead should 
be given to each edge of the valve so that it will be necessary to 
lengthen the eccentric rod B 1 , -^" -f- £"=-^" to get the valve 



HANDBOOK ON ENGINEERING. ,317 

into its proper position. A little reflection will show the reason 
for lengthening the eccentric rod B 1 . In speaking of the front 
and back centers, they are taken to coincide with the crank and 
head ends of the cylinder. When the piston is at the crank end 
of the cylinder, the crank is on the front center. By referring to 
the log it will be seen that to adjust the backward eccentric rod 
B, it will also be necessary to lengthen it. The valve is |" blind 
on the front center and has | " lead on the back center. The 
total lead is, therefore, |" minus J"= J". One-half J"=:|", 
which being added to the amount the valve is lapped on the front 
center, makes J", or the amount the eccentric rod B will have to 
be lengthened to make the valve open equally at each end of the 
piston stroke. The opening the valve has when the crank is on 
the centers is called the. lead and in the case of the backward 
motion, it is found that after the eccentric rod is lengthened, the 
lead is J", which is too much for most cases and in this one we 
can assume that ^V" would be about right. 

Before explaining the adjustment of the eccentric for the cor- 
rect angular advance, it will be in order to call attention to the 
necessity of making the adjustment for the eccentric rod lengths 
first. The eccentric rods are lengthened or shortened, as the 
case may require, by inserting or removing liners between the 
eccentric rods and straps at R. Other forms of construction 
provide different means for adjustment, but the principle is the 
same in each. It will be noted that the correct length for the 
two motions is obtained by adjusting the eccentric rod corre- 
sponding to that motion. Any attempt to correct an irregularity 
by changing the length of the valve rod F will result erroneously, 
unless both eccentric rods require the same amount of movement 
and in the same direction. After having adjusted the eccentric 
rods to the correct lengths, the angular advance of the eccentric 
A can be changed. Place the crank on a dead center and have 
the reverse lever thrown in the backward motion and then 



318 , HANDBOOK ON ENGINEERING. 

loosen the set screws that hold the eccentric to the shaft and tarn 
it towards the crank until the valve shows open ^", and then 
tighten the set screws on the shaft. After all the adjustments 
have been effected, it is always advisable to turn the engine over 
again and catch all the dead centers, so that the correctness of 
the adjustments can be verified. After taking the new log, it 
will usually be found that some slight irregularities have been 
introduced, especially if any of the adjustments have been consid- 
erable, as the changes made for one motion will affect the other 
slightly. 

The link motion shown in the cut is so connected that the lead 
increases as the link is shifted towards the center. If the eccen- 
tric rods be oppositely connected to the link, the engine will run 
in an opposite .direction for a given reverse lever position and the 
lead will decrease as the lever is shifted towards the center. The 
link motion for hoisting engines is quite commonly connected in 
this manner, for the reason that the engine will stop when the 
lever is put on the center, which is not the case when connected 
as shown. Of course, in such a case, the admission and cut-off 
take place at the same position in the stroke and the compression 
is high, but with a light load the engine will run on the center, 
which is considered objectionable in the case of the hoisting 
engine. 

VALVE=SETTING FOR ENGINEERS. 

Plain slide-valve* — The plain slide-valve, while the simplest 
valve made, is perplexing to one who has not made a study 
of it. Unless one understands the principles . of the valve 
and its connections, he will probably meet with trouble when he 
attempts to set it. We will first place the engine (see p. 195) 
on the dead center, and will simply i explain the other steps 
that have to be taken. In the first place, it should be understood 
what result is obtained by adjusting the position of the eccentric 



HANDBOOK ON ENGINEERING. 319 

and the length of the valve stem. The position of the eccentric, 
when the valve is set, depends upon which way the engine is to 
run and whether the valve is connected directly to the eccentric 
or whether it receives its motion through a rocker which reverses 
the motion of the eccentric. When the valve is direct connected, 
the eccentric will be ahead of the crank by an amount equal to 90°, 
plus a small angle called the angular advance. When a reversing 
rocker is used, the eccentric will be diametrically opposite this 
position, or it will have to be moved around 180° and will follow 
instead of lead the crank. Shifting the eccentric ahead has the 
effect of making all the events of the stroke come earlier, and 
moving it backwards has the effect of retarding all the events. 
Lengthening or shortening the valve stem cannot hasten or retard 
the action of the valve, and its only effect is to make the lead or 
cut-off, as the case may be, greater on one end than on the other. 
The general practice is to set a slide-valve so that it will 
have equal lead. The lead is the amount that the valve 
is open when the engine is on the center. To set the valve, 
therefore, put the engine on the center, remove the steam-chest 
cover so as to bring the valve into view, and adjust the eccentric 
to about the right position to make the engine turn in the direction 
desired. Now make the length of the valve-spindle such that the 
valve will have the requisite amount of lead, say T x g of an inch, 
the amount, however, depending upon the size and speed of 
the engine. Turn the engine over to the other center and measure 
the lead at the end. If the lead does not measure the same as 
before, correct half the difference by changing the length of the 
valve-stem, and half by shifting the eccentric. Suppose, for 
example, that the lead proved to be too great on the head end by 
half an inch. Lengthening the valve-stem by half of this, or \ 
inch, would still leave the lead \ inch too much on the crank 
end. . That. is to say, the valve would then open too soon at both 
head and crank ends, and to correct this, the eccentric would 



320 HANDBOOK ON ENGINEERING. 

have to be moved back far enough to take up the other quarter- 
inch. Sometimes it is not convenient to turn the engine over by 
hand, in which case the valve may be set for equal lead as fol- 
lows: To obtain the correct length of the valve-stem, loosen the 
eccentric and turn it into each extreme position, measuring the 
total amount that the valve is open to the steam ports in each 
case. Make the port opening equal for each end by changing the 
strength of the valve-stem. This process will make the valve- 
stem length as it should be. Now put the engine on a center and 
move the eccentric around until the valve has the correct lead and 
fasten the eccentric in that position. This will determine the 
angular advance of the eccentric. 

The plain slide valve* — The function of the slide-valve is 
to admit steam to the piston at such times when its force can be 
usefully expended in propelling it, and to release it when its pres- 
sure in the cylinder is no longer required. Notwithstanding its 
extreme simplicity as a piece of mechanism, no part of the engine 
is more puzzling to the average engineer when the problem to be 
solved is to determine beforehand the results which will be pro- 
duced by a given construction and adjustment, or the proportions 
and adjustment required to produce given results. All who have 
had any experience in constructing and setting slide-valves are 
aware, in a general way, that the events of the stroke cannot 
be independently adjusted ; for instance, a cut-off earlier than 
about § of the stroke. 

To set a slide valve* — The valve should be set in such a man- 
ner that when the engine is on the dead center, the part admitting 
the steam to the cylinder is open a small amount, as shown in Fig. 1, 
which is called lead. The object of lead is to enable the steam 
to act as a cushion against the piston before it arrives at the end 
of the stroke, to cause it to reverse its motion easily, and also to" 
supply steam of full pressure to the piston the instant it has passed 
dead center. The lead required varies in different engines from 



HANDBOOK ON ENGINEERING. 



321 



Fig. 1 also shows the 
position of eccentric, which should always be set ahead of the 

AT POINT OF TAKING STEAM. 




Fig. 1. 

crank at an angle of 90°, plus another augle called the " angular 
advance." When the valve is to have lead the angular advance 
must be a little greater than when no lead is desired. 




Fig. 2. 



Fig* 2 shows the position of eccentric at point of cut-off ; also 
position of Piston. 



POSITION WHEN COMPRESSION BEGINS. 




Fig. 3. 

Fig* 3 shows position of valve when compression begins. It 
also shows position of eccentric. The compression at the left 



322 



HANDBOOK ON ENGINEERING. 



end, towards which the piston is moving, has just commenced, 
and the exhaust is about to take place from the other end. 
AT POINT OF TAKING STEAM. 




Fig. 4. 

Fig-. 4 shows the position of eccentric and valve in an engine 
with a rocker-arm. 

I AT POINT Or CUT-OFFT 




Fig. 5, 
Fig, 5 shows the position of valve and eccentric at point of 
cut-off. 

pqsrr/OA/ when compression begins. 




Fig. 6. 

Pig. 6 shows point of compression. 



HANDBOOK ON ENGINEERING. 323 



CHAPTER XIII. 

TAKING CHARGE OF A STEAH POWER PLANT. 

It is frequently the case that an engineer, on assuming charge 
of a steam power plant, proceeds as though he were thoroughly 
familiar with the condition of the engine, boiler and entire sur- 
roundings. He plunges headlong into his duties, without first 
taking his bearings. A skillful physician on taking a case, would 
not proceed in this manner ; neither would a lawyer. The physi- 
cian would feel the patient's pulse, look at his tongue, take his 
temperature, observe his color and ask a number of questions, all 
for the purpose of enabling him to make a correct diagnosis of 
the patient's ailment. The first duty of an engineer, when he 
takes charge of a plant, is to ascertain the arrangement and con- 
dition of the plant. Since the boiler is the most important mem- 
ber of the plant; it should be the first to engross his attention, and 
it, together with its connections, should be examined as closely as 
time and surrounding conditions will permit. He should look the 
boiler all over, internally and externally, if possible, in view of 



324 HANDBOOK ON ENGINEERING 

mud, scale, grooving, pitting and defective braces. The furnace 
should be examined next, in view of burnt-out brickwork, grate 
bars and door linings. It may be that the furnace has distorted 
or cramped proportions, or it may be too large. The bridge wall 
may be so constructed as to huddle the flames in one spot on the 
fire sheets of the boiler ; or it may be of such shape and in such 
condition as to cause the ignited gases to become dissipated in 
the combustion chamber. Even the combustion chamber itself 
may require the service of a bricklayer. He should next examine 
the safety valve and see that it is of ample capacity to relieve the 
boiler of surplus steam, and that it is in thorough working order. 
The first duty of an engineer when entering his plant' at any 
time, is to ascertain how the water in the boiler stands, or, 
in other words, just how much water the boiler contains. He 
should open the gauge cocks first and note what comes from each 
in turn ; then open the cocks or valves connecting the glass gauge 
and note the water line there shown. He should also blow the 
water column out, in case any sediment may have choked any of 
the passages, which would be liable to give a false impression as 
to the actual quantity of water contained in the boiler. Should 
the water be found at the correct height, he may now proceed to 
get up steam; open the damper, pull down the banked fire and 
spread it evenly over the grate, adding a quantity of green fuel. 
Allow the steam to rise slowly ; do not force it. This applies 
especially to raising steam in a boiler which has been cold, as the 
expansion of the parts of the boiler due to the heat should take 
place slowly and evenly; otherwise, the life of the boiler will be 
shortened. While waiting for the steam to come up to the desired 
point, the engineer should now get his engine ready for the day's 
run. Fill all the oil cups and cylinder lubricator, so as to be 
ready to operate as the engine starts. With a hand oil squirt 
can, go around all the small brasses, connections, etc., and, in,a 
word, well lubricate all the parts where friction takes place. If 



HANDBOOK ON ENGINEERING. 325 

you have an oil pump for your cylinder and valves, it would be 
well to inject a small quantity of cylinder oil before the engine is 
started, while the stop-valve is open, during the time the engine is 
being " warmed up." After the engine cylinder is warmed 
through, the lire should again be looked at, and dealt with 
according to the indications. Of course, the water gauge glass 
must be looked at frequently, not only while raising steam in the 
morning, but at all times while the boiler is in operation. 

Everything- being in readiness, the engine is started slowly at 
first, the speed being gradually increased until the limit is reached. 
The day's run is now fairly commenced. A boiler should be 
blown down one gauge every morning before starting the day's 
run to get rid of the mud, scale or anything that is held in 
mechanical suspension in the water. Before starting in the 
morning and at noon is the best time to do this, as the sediment 
has settled to the bottom during the night, after the circulation 
of the water has stopped. When blowing a boiler down, always 
remember to open the blow- valve slowly — be careful not to blow 
too long, and then to close the valve slowly. 

An engineer or attendant cannot be too careful in handling 
the many appliances with which a steam plant is equipped. The 
principal things to which an engineer should give his attention 
during the operation of his boiler day by day are, as follows : 
The maintenance of the water at the proper level, as near as pos- 
sible, and avoiding fluctuations in the pressure of steam. See 
that the firing is done correctly and economically so as to obtain 
from every pound of coal all that is possible under the con- 
ditions existing. The raising of the safety valve from its seat, 
at least once daily ; the blowing out of the water column twice 
daily, or ofteuer, if the water used is very dirty ; the frequent 
opening of the water gauge cocks, or try cocks, as they are 
sometimes called, and not depending entirely on the gauge glass 
for the correct height of water ; the blowing down of the boiler 



326 HANDBOOK ON ENGINEERING. 

one gauge every day; the keeping of all valves, cocks, fittings, 
steam and water-tight, clean and in good working order. 

When shutting down the plant for the night, the lires should 
be cleaned out and the live coals shoved back on the grates and 
banked ; that is, green coal should be thrown upon them, suffi- 
ciently thick to cover all the glowing fuel. Pump in the water 
until it reaches the top of the glass gauge. This should be done 
to insure a sufficient quantity from which to blow down in the morn- 
ing, and also to allow for any small leaks. Then close the cocks or 
valves connecting the glass gauge. Should this glass break dur- 
ing the night and the valves be left open, there would not be much 
water to start with in the morning. Leave the damper open a 
little, just sufficient to allow the gases which will rise from the 
banked fires to escape up the chimney. Finally, make sure that 
all the valves about the plant which should be closed, are closed ; 
and all those which should be left open, are open. Of course, 
the foregoing is applicable to a plant where there is no night 
engineer. But in any case, no matter how many assistants an 
engineer may have under his control, he should be familiar with 
all details of the plant under his charge. 

One of the most important points in connection with the opera- 
tion of a steam boiler, is the preventing of corrosion, both 
internally and externally. One of the best aids to secure the 
well working and longevity of the steam boiler, or, in fact, the 
whole plant, is by being regular and punctual in a certain course 
of treatment, which has been proven to be effectual and beneficial 
in its results. All conditions do not require the same methods of 
treatment; therefore, it is absolutely necessary that the engineer 
in charge familiarize himself with all the conditions under whkjh 
his plant is running, for then, and then only, can he intelligently 
prescribe and act accordingly. Above all, let him remember 
the adage, " Eternal vigilance is the price of safety/* especially 
where a steam boiler is concerned. 



HANDBOOK ON ENGINEERING. 327 

ECONOMY IN STEAM PLANTS. 

In these days of close figuring upon expense in office buildings 
and manufacturing plants, what may at first appear insignificant 
items may actually make all the difference between a good margin 
of profit and an actual loss. 

The fuel expense is one of the largest in the operation of the 
majority of plants, and any reduction which can be made in the 
amount of fuel used, while maintaining the same amount of power, 
is considered a direct gain. The evaporation of more than' nine 
pounds of water per pound of coal, is looked upon with suspicion 
by many, as it is not thought possible to obtain more than this 
amount in even the best designed and well regulated furnaces and 
boilers, especially when the firing is done by hand. The actual 
value of the fuel depends upon the way in which it is used, fully 
as much as on any other factor. The heat unit in the coal should 
be as much as possible utilized, as in one pound of good steam 
coal there is about 14,000 B. T. U., and about 10,000 of this 
amount can be utilized, so that 4,000 heat units are lost. The 
mixture of gases in a furnace depends upon the amount of ab- 
used. One pound of coal requires, theoretically, about twelve 
pounds of air to burn completely. But, in practice, about twice 
this amount is required in the present boiler furnace. To have 
good combustion coal requires a good draft. The gases are con- 
sumed near the fire, and the waste gases carry the heat to the 
boiler on their way to the stack. The boiler ought to have suffi- 
cient heating surface, or the hot wasted gases ought to travel a 
sufficient distance to be cooled down to about 350 degrees Fah- 
renheit ; which temperature is found high enough to produce a 
good draft in a stack of, at least, 100 feet high. 

How a bad draft will unnecessarily increase the coal bill, is 
this: That of all the fuel burnt to perform certain work, ascer- 
tained proportion is consumed to keep the heat of the furnace up 



328 HANDBOOK ON ENGINEERING. 

to say, 212 degrees Fahr,, without making aiiy steam whatever 
which is available for work. This quantity varies from 20 to 30 
per cent, according to conditions, which are affected by various 
causes, such as leakages of steam, air, or water. Now, the only 
available power for work which we get from our fuel is the margin 
between this, say thirty per cent required for the said purpose, 
and what we generate above that. An engineer should notice the 
general condition of his boiler or boilers, and the equipments of 
same; he should examine the boiler both inside and outside, 
ascertain the dimension of grates, heating surfaces, and all im- 
portant parts. The area of heating surfaces is to be computed 
from the outside diameter of water-tubes, and the inside diameter 
of fire-tubes. All the surfaces below the main water level which 
have water on one side and products of combustion on the other, 
are to be considered as water-heating surfaces. If he finds that 
the boiler does not come up to what he thinks it should, he should 
put the boiler and all its, appurtenances in first-class condition. 
Clean the heating surfaces inside and outside of boiler, remove 
all scale from flues and inside of boiler ; remove all soot 
from inside of flues, all ashes from the flame-bed or com- 
bustion chamber, and all ashes from smoke connections. Close 
all air leaks in the masonry and poorly fitted cleaning door. 
See that the damper in britching or smoking-flue will open wide 
and close tight. Test for air leaks through the crevices, by 
passing the flame of a candle over cracks in the brick work. A 
good, attentive fireman, who understands his business and will 
keep his bars properly covered without choking his fires, is really 
worth double the wages of an ignorant or inattentive one, as his 
coal bills would certainly prove. All an engineer can do is to 
keep the steam piston and valve or valves tight. Also the drains 
from his engine, and all drains on steam traps in the plant tight ; 
also, his engine cleaned and well-oiled, and not keyed up too tight. 
If in a heating plant, he should see that the back pressure valve is 



HANDBOOK ON ENGINEERING. 



329 



afe all times tight, as it does not take much of a leak to show a 
difference in his coal bill at the end of a month. He should keep 
all valves in the pumps in his plant tight, and see that the pump 
piston is packed, but not too tight. After a pump is packed, you 
should be able to move it back and forth by hand ; if the pump 
valves leak he can take them out and smooth them up with sand- 
paper. He should see that the feed-water to the boiler is at least 
208 degrees Fahrenheit ; if it is under 204 degrees, his heater is not 
right, as the poorest heater will heat the feed-water to 204 ; it 
would be well to overhaul the heater — it may be full of scale ; or, 
if an open heater, the spray may be off. In most first-class 
plants, the feed-water is 212 Fahrenheit. 

PRIMING. 

The term priming is understood by engineers to mean the 
passage of water from the boiler to the steam cylinder, in the 
shape of spray, instead of vapor. It may go on unseen, but it is 
generally made manifest by the white appearance of the steam as 
it issues from the exhaust-pipe as moist steam, which has a white 
appearance aud descends in the shape of mist, while dry steam 
has a bluish color arid floats away in the atmosphere. Priming 
also makes itself known by a clicking in the cylinder, which is 
caused by the piston striking the water against the cylinder head 
at each end of the stroke. Priming is generally induced by a 
want of sufficient steam-room in the boiler, the water being car- 
ried too high, or the steam-pipe being too small for the cylinder, 
which would cause the steam in the boiler to rush out so rapidly 
that, every time the valve opened, it would induce a disturbance 
and cause the water to rush over into the cylinder with the steam. 



330 



HANDBOOK ON ENGINEERING. 



TABLE OF PROPERTIES OF SATURATED STEAM. 



£ 

a *•£ a 
•~ a> 2 © 

© P/J3 S3 
lilt 

<s a a o 


© 
© 2 a 

ft t»C© 

3^5 


Total heat 
in heat units 
from water 
at 32°. 


2 

'3 

Cf 

•rHCO — 

c3 a 


;at of vapor - 
tion or 
ent heat in 
at units. 


msity or 
sight of a 
bicfoot in 
unds. 


© 

«h<o © 

© a o 

a s-a 


ctor of 
uivalent * 
aporation 
212°. 


© 
a 

00 

a a 

— <u a 
o3 > a 
*? o © 


Ph Am c3 


© _. aj 


M«§.2 


wJS.3 


p£g£ 


£§.s 


03 c^O+a 
fr © © OS 


©.a o3 


1 


101.99 


1113.1 


70.0 


1043.0 


00299 


334.5 


.9661 


1 


'2 


126.27 


. 1120 5 


94.4 


1026.1 


0.00576 


173 6 


.9738 


2 


3 


141.62 


1125.1 


109.8 


1015.3 


0.00844 


118.5 


.9786 


3 


4 


153 09 


1128.6 


121 4 


1007 2 


0.01107 


90 33 


.9822 


4 


5 


162.34 


1131 5 


130.7 


1000 8 


01366 


73.21 


.9852 


5 


6 


170.14 


1133.8 


138 6 


995.2 


0.01622 


61 65 


.9876 


6 


7 ■ 


176 90 


1135.9 


145.4 


990.5 


01874 


53.39 


.9897 


7 


8 


182 92 


1137.7 


151.5 


986 2 


0.02125 


47.06 


.9916 


8 


9 


188.33 


1139 4 


256.9 


982.5 


0.02374 


42 12 


.9934 


9 


10 


193.25 


1140 9 


161 9 


979 


02621 


38.15 


.9949 


10 


15 


213 03 


1146.9 


181 8 


965,1 


0.03826 


26.14 


1.0003 


15 


20 


227 95 


1151.5 


196.9 


954 6 


0.05023 


19 91 


1.0051 


20 


25 


240.04 


1155.1 


209 1 


946.0 


0.06199 


16.13 


1 0099 


25 


30 


250 27 


1158.3 


219 4 


938 9 


07360 


13.59 


1.0129 


30 


35 


259.19 


1161.0 


228.4 


932.6 


08508 


11.75 


1.0157 


35 


40 


267 . 13 


1163 4 


236 4 


927.0 


0.09644 


10.37 


1.0182 


40 


45 


271-29 


1165.6 


243.6 


922.0 


0.1077 


9.285 


1.0205 


45 


50 


280.85 


1167 6 


250.2 


917 4 


1188 


8.418 


1.0225 


50 


55 


286 89 


1169 4 


256.3 


913 1 


0.1299 


7698 


1.0245 


55 


60 


292.51 


1171.2 


261 9 


909 3 


1409 


7.097 


1.0263 


60 


65 


297.77 


1172.7 


267.2 


905.5 


0.1519 


6 583 


1.0280 


65 


70 


302 71 


1174.3 


272.2 


902.1 


0.1628 


6.143 


1.0295 


70 


75 


307 38 


1175.7 


276.9 


898 8 


0.1736 


5.760 


1.0309 


75 


80 


311 80 


1177.0 


281.4 


895.6 


0.1843 


5.436 


1.0323 


80 


85 


316.02 


1178 3 


285.8 


892.5 


0.1951 


5 126 


1 0337 


85 


90 


320 . 04 


1179.6 


290 


889 6 


0.2058 


4.859 


1.0350 


90 


95 


323.89 


1180.7 


294.0 


886 7 


0.2165 


4.619 


1.0362 


95 


100 


327.58 


1181.9 


297.9 


884.0 


0.2271 


4.403 


1.0374 


100 


105 


331 13 


1182.9 


301 6 


881 3 


2378 


4.206 


1.03S5 


105 


' 110 


331 56 


1184 


305 2 


878 8 


2484 


4.026 


1 0396 


110 


115 


337.86 


1185 


308.7 


876 3 


0.2589 


3 862 


1.0406 


115 


120 


341.05 


1186.0 


312.0 


874.0 


0.2695 


3.711 


1 0416 


120 


125 


344 . 13 


1186.9 


315.2 


871.7 


0.2800 


3.571 


1.0426 


125 


130 


347.12 


1187 8 


318.4 


869 4 


0.2904 


3.444 


1.0435 


130 


140 


352.85 


1189.5 


324.4 


865 1 


3113 


3 212 


1 0453 


140 


150 


358.26 


1191.2 


330.0 


861.2 


3321 


3.011 


1.0470 


150 


160 


363.40 


1192.8 


335.4 


857-4 


3530 


2 833 


1.0486 


160 


170 


368 29 


1194.3 


340.5 


853 8 


0.3737 


2.676 


1.0502 


170 


180 


372.97 


1195.7 


345.4 


850.3 


0.3945 


2.535 


1.0517 


180 


' 11)0 


377.44 


1197.1 


350 . 1 


847 


0.4153 


2.408 


1.0531 


190 


200 


381.73 


1198.4 


354.6 


843 8 


0.4359 


2.294 


1 0545 


200 


225 


391 . 79 


1201.4 


365.1 


816.3 


0.4876 


2.051 


1 0576 


225 


250 


400.99 


1204.2 


374.7 


829.5 


0.5393 


1.854 


1.0605 


250 


275 


409 50 


1206.8 


383.6 


823 2 


0.5913 


1.691 


1 0632 


275 


300 


417.42 


1209.3 


391 9 


817 4 


0.644 


1 553 


1 0657 


300 


325 


424.82 


1211.5 


399 6 


811 9 


0.696 


1 437 


1.0680 


325 


350 


431 90 


1213.7 


406.9 


806.8 


0.748 


1.337 


1 0703 


350 


375 


438 40 


1215.7 


414 2 


801 5 


0.800 


1.250 


1.0724 


375 


400 


445.15 


1217.7 


421.4 


796 3 


0.853 


1.172 


1 0745 


400 


500 


466.57 


1224.2 


444.3 


779.9 


1.065 


.939 


1.0812 


500 



HANDBOOK ON ENGINEERING. 331 

The gauge pressure is about 15 pounds (14.7) less than the 
total pressure, so that in using this table, 15 must be added to 
the pressure as given by the steam gauge. To ascertain the 
equivalent evaporation at any pressure, multiply the given evap- 
oration by the factor of its pressure, and divide the product by 
the factor of the desired pressure. Each degree of difference in 
temperature of feed-water makes a difference of .00104 in the 
amount of evaporation. Hence, to ascertain the equivalent 
evaporation from any other temperature of feed than 212°, add to 
the factor given as many times .00104 as the temperature of 
feed-water is degrees below 212°. For other pressures than those 
given in the table, it will be practically correct to take the pro- 
portion of the difference between the nearest pressures given in 
the table. Example : If a boiler evaporates 3000 lbs. of water 
per hour from feed-water at 200 degs. Fah. into steam at 100 
lbs. per sqr. in. by the gauge, what is the equivalent evaporation 
" from and at" ? Ans. 3159.24 lbs. 

Operation : Temperature of feed-water = 200 degs. 

Then, 212 — 200 = 12 = difference in temperature. 

Then, 15 added to the gauge pressure = 115. 

Looking in the above table we find the factor 1.0406. 

Then, .00104 X 12= .01248. 

And, 1.0406 
.01248 
1.05308 

Then, 3000 X 1.05308 = 3159.24 lbs. the equivalent evapo- 
ration. 

The H. P. of this boiler would be 91.57. 



332 HANDBOOK ON ENGINEERING. 

HIGH PRESSURE STEAM. 

It is generally believed that high-pressure steam is cheaper to 
use and costs but little more to generate than low pressure steam. 
A study of a table of the properties of saturated steam, to be 
found on another page in this book, will show why high-pressure 
steam is economical to generate, and a few calculations will 
prove instructive by showing what may be excepted from its use. 
To generate one pound of steam at 25 lbs. pressure, absolute, 
requires an expenditure of 1,155 thermal units, and to generate 
steam at 200 lbs. pressure, absolute, requires 1,198 thermal units, 
or an increase of only 43 thermal units for an increase of 175 lbs. 
pressure. Further investigation shows that the temperature of 
steam at 25 lbs. pressure is 240° and at 200 lbs. pressure, 382°, 
the difference, 142, being the number of degrees that the tem- 
perature of steam is raised with an expenditure of 43 thermal 
units. To put it in another way, the temperature of the steam 
has been raised nearly 60 per cent, with an increase of less 
than 4 per cent in the number of thermal units. It is con- 
venient to consider that the generation of steam takes place 
by two different steps, one of which is raising the water from 
32° to the temperature corresponding to the pressure of the 
steam, and the other is giving off the steam at this pressure, 
which process absorbs a quantity of heat that becomes latent 
or non-sensible. At 25 lbs. pressure, the sensible heat 
required 'to raise one lb. of water from 32° to 240° is 
209 units, and to raise it from 32° to 382 degrees, the 
temperature of steam at 200 lbs. pressure requires 355 thermal 
units. The increase in the sensible heat of the water, there- 
fore, is 355 minus 209 = 146 units, or about the same as the tem- 
perature increase for these two pressures, which is 142°. It is thus 
clear that the total increase in the number of heat units in steam 
raised from 25 His. to 200 lbs. pressure is small (43° as found 



HANDBOOK ON ENGINEERING. 333 

because the latent heat absorbed in the formation of the 
steam decreases as the pressure increases. It requires less heat 
to generate steam from water raised to 382° at 200 lbs. pressure, 
than from water previously raised to 240° at 25 lbs. pressure. 
To generate higher pressure steam, therefore, we must first 
apply enough heat to bring the water to a temperature 
corresponding to the higher pressure. This heat will be 
nearly proportionate to the increase in temperature. Then 
enough heat must be applied to the water to generate the steam, 
the amount of heat required for this purpose decreasing as the 
pressure increases. The combined result of these two processes 
is that it takes only a very small increase in the total heat to pro- 
duce the higher pressure steam. The idea may be suggested that 
if this higher pressure is obtained at the cost of so small an expen- 
diture of heat, it would not be reasonable to expect a large gain 
in economy from it, since it is not possible for the steam to do a 
greater amount of work than the equivalent of the heat which it 
contains. This would be true were it not for the fact that the 
larger part of the heat in the steam is rejected during the ex- 
haust. To illustrate, suppose an engine to exhaust at atmos- 
pheric pressure, or at about 15 lbs., absolute, and that the steam 
is saturated. As may be determined from the steam tables, there 
would be ejected 1,147 heat units per pound of steam, or 51 
heat units less than were found to be in a pound of steam at 
200 lbs. pressure. That is to say, under the above assumption, 
there are available only 51 heat units per pound of steam to do 
the work in the engine cylinder when the steam pressure is 200 
lbs. But we also found that the increase in the heat units in 
raising the steam pressure from 25 to 200 lbs. was 43, and hence 
the increase in proportion to the number available is large, 
although the increase in proportion to the total number required 



334 HANDBOOK ON ENGINEERING. 

to generate the steam is .small. This shows why high-pressure 
steam is economical to generate and profitable to use. It should 
be stated that the only way in which the full benefit can be de- 
rived from high pressure-steam is by using the steam expansively, 
keeping the terminal pressure at release as low as possible. I 
will not take the space to give the calculations to prove this, 
but will compare a few results of calculations. Suppose steam 
to be used in a theoretically perfect engine at the pressure 
of 25 lbs., 50 lbs., 100 lbs. and 200 lbs. We will assume that 
in each case the cut-off is at one-third stroke, giving three 
expansions and a terminal pressure of one-third the initial pres- 
sure. The steam consumptions will then be, respectively, about 
16J, 16, 15*, and 14 lbs. per horse-power, showing that gain 
from the increase in pressure is very slight. On the other hand, 
* suppose the expansions to be carried to the atmospheric pressure 
in each case. The consumptions will then be about 27, 15, 11 
and 8 lbs. respectively, showing a marked decrease. 

Still another point should be mentioned in relation to the 
relative gain that is to be expected with the increase in pressure. 
Comparing the last figure, it will be observed that the decrease 
in consumption when the pressure increased from 25 to 50 lbs- 
was 27 minus 15 = 12 lbs., or 44 per cent. Again, when 
the pressure doubled from 50 to 100 lbs., the consumption 
decreased only 4 lbs., or 27 per cent; and when the pressure was 
again doubled to 200 lbs., the consumption only decreased 3 lbs., 
or about 27 per cent. It is evident from this that the saving 
from an increase in steam pressure grows less as the pressure 
increases, and this is found to be the case in actual practice. 
There is another reason for this, also, coming from the losses 
incident to cylinder condensation and re-evaporation, which is 
more marked where there is a wide range in pressures than where 
the pressures are more uniform throughout the stroke. It is found 
that where the steam pressure is much above 100 lbs. gauge pres- 



HANDBOOK ON ENGINEERING. 335 

sure, no gain will result from a further increase in pressure with- 
out compounding, the advantage of the compound engine being 
that the extremes of temperature in the cylinders are not so great 
as with a simple engine. * 

USING STEAH FULL STROKE. 

The steam engine is nothing in the world but an enlargement 
upon the end. of the steam pipe, containing a piston against 
which the steam in the boiler may press. The piston moves a 
certain distance, and then the steam is allowed to press upon its 
other side, while the steam on the first side is allowed to flow into 
the atmosphere and go to waste. The slide-valve is the device or- 
dinarily employed to admit the steam, alternately, to opposite sides 
of the piston, and to permit the free outflow of steam from the 
reverse side of the piston. As the steam presses upon the piston 
the piston moves forward with a force equal to the pressure of 
steam per square inch, multiplied by the number of square inches 
of piston surface. Steam occupies the entire space from the sur- 
face of the water in the boiler, to the piston of the engine. The 
steam space, therefore, includes the steam space of the boiler, the 
steam pipe, the steam chest, and the cylinder space upon one side 
of the piston. As the piston moves, the entire steam space be- 
comes a little larger, by reason of the C}dinder space becoming 
longer. Thus it will be seen that all of the steam in the boiler 
and pipe and engine, would expand a trifle and the pressure 
become somewhat reduced, were it not for the fact that new 
steam is made by the fire as fast as the piston moves forward. 
By this means the steam is maintained at about uniform pressure. 
It will be seen that the pressure is produced upon the piston 
by the generation of new steam from the water, that is, the fire 
causes the water to generate a quantity of steam, and this quantity 
of steam forces its way into the other steam, exerting a force 
upon the whole body of steam and pushing the piston ahead, 



33(5 HANDBOOK ON ENGINEERING. 

If an engine piston has a surface of 100 square inches and 
a stroke of ten inches, it follows that the piston will yield a 
thousand cubic inches additional steam space by its movement 
during one stroke, and consequently, the fire will be called upon 
to produce 1,000 cubic inches of new steam for each single stroke 
of the engine. If the pressure of the steam be eighty pounds to 
the square inch, the engine piston will move with the force of 
8,000 pounds. When the engine has completed one stroke, we 
find an amount of power exerted equal to 8,000 pounds moved 
ten inches, and we then open the exhaust valve and empty into 
the atmosphere 1,000 cubic inches of eighty-pound steam. We 
keep on doing this for each stroke. Now your attention is par- 
ticularly called to the fact that when we empty the steam out of 
the cylinder, it is just as good as when it went into the cylinder ; 
that is, it was 1,000 cubic inches of steam at a pressure of eighty 
pounds to the square inch, and when it goes into the atmosphere 
it will expand into over 6,000 cubic inches, at fifteen pounds 
pressure to the square inch, or the same pressure as the atmos- 
phere. This 1,000 cubic inches of steam which we clumped out 
of the cylinder, is precisely the same quality of steam as the 
steam which we have penned up in the boiler ; and which we have 
to be making new all the time in order to keep the engine run- 
ning. Such is the operation of the steam engine which receives 
its steam the full length of the stroke ; and such an engine may 
be described briefly, as a very wasteful machine which throws 
away steam as good as it receives it, and which requires the gen- 
eration of a cylinder full of full pressure steam for each stroke. 
It should be readily understood that when the piston has com- 
pleted its stroke, and just before the exhaust valve is opened to 
allow the steam to escape, the cylinder contains 1,000 cubic 
inches of steam at eight}' pounds pressure, which it is capable of 
expanding into many thousand cubic inches at constantly de- 
creasing pressure. The first step in the improvement of such an 



HANDBOOK ON ENGINEERING. 337 

engine would be to so arrange things as to get some benefit from 
this enormous power of expansion. The full stroke engine does 
not get one-half of the power before it throws the steam away. 
The engine which we would have referred to would yield a power 
of 8,000 pounds moved ten inches at each single stroke; 33,000 
pounds moved one foot in one minute is a horse-power ; 66,000 
pounds moved half a foot would be the same. An engine using 
steam full stroke is such an extravagant contrivance that we, now- 
adays, seldom find them in use. There are certain classes of 
engines built, fitted with link motions for driving the valve, and 
they are arranged so as to carry their steam full stroke, but pro- 
vision is also made for quickly hooking up the link and suppress- 
ing the full-stroke feature. 

SLIDE VALVE ENGINES. 

If we have an engine arranged to receive its steam full stroke 
and to dump the steam out into the air in as good condition as it 
was received, and we wish to get some of the benefits of the 
expansive power of the steam, there is a simple way of doing it 
and without any great change in the engine, and that is, to 
lengthen out the slide valve so that after the cylinder is half full 
of steam, the valve will shut and let no more steam enter. Dur- 
ing the balance of the stroke, the entire power conies from the 
gradual expansion of the steam shut up in the cylinder, and it 
will be readily seen that whatever power we succeed in getting out 
of the expansion of the steam, is pure gain. The lower the pres- 
sure of the steam is when it is exhausted into the air, the more it 
has expanded, the more power we have gotten out of it, and the 
more we have gained. It may be said in a few words, that all 
slide-valve engines are now arranged to work their steam expans- 
ively. But it is, unfortunately, found that the slide-valve pos- 
sesses a peculiar defect which prevents the system being carried 
very far. We can lengthen out a slide-valve so as to cut the 

22 



338 HANDBOOK ON ENGINEERING. 

steam off at any desired point of the stroke, and we must then 
increase the throw of the eccentric in order to properly operate 
the long valve. But the minute we do this we find that we have 
interfered, to a certain extent, with the proper operation of the 
exhaust. No matter what we do about the admission of steam or 
about cutting off before the end of the stroke, we must arrange 
our exhaust to take place at a certain point at the end of the 
stroke. It is found in practical operations that this necessary 
quality of the slide-valve prevents our arranging it to cut off the 
steam properly at an earlier point than about five-eighths or three- 
quarter stroke. The consequence is, that an engine with two-feet 
stroke will receive steam 18 inches, then have 6 in. of expansion. 
It may be fairly said, in a general way, that about all the slide- 
valve engines now manufactured, cut off the steam at about five- 
eighths or three-quarters stroke ; and it may be further said that this 
is about all we can get out of a slide-valve engine. Even the trifling 
expansion got from such engines as this, represents an immense 
amount of money in the course of a year in large establishments, 
but it is not good enough for anyone who seeks even a decent 
investment of money, in power-getting appliances. 

REGULAR EXPANSION ENGINES. 

A liberal expansion of steam being desirable and the slide- 
valve proving totally incapable of providing for such expansion, 
the first step in the desired direction is to totally discard the 
slide-valve. The Corliss valve is a cylindrical piece, oscillating 
in a cylindrical hole. The valve does not fill this hole, but seats 
against one side only. Hence, the fitting qualities are about the 
same as with the slide-valve and, in fact, the principle is about 
the same, the Corliss representing a portion of the slide-valve, 
rolled into the form of a cylinder and operating in a concave seat. 
We must not only discard the slide-valve arrangement, but in 
the valve arrangement which we select, we must secure an abso- 



HANDBOOK ON ENGINEERING. 339 

lute independence between the steam admission part of the sys- 
tem and the exhaust part. The slide-valve is one chunk of cast 
iron, letting in and cutting off steam at its outside edges, and 
opening and closing the exhaust by its inside edges. When one 
of these valve edges moves, everything else has to move. There 
is, consequently, no independence of action. In the Corliss 
engine there are parts to let steam into the cylinder and to quit 
letting it in at the proper time, and there are valves to let it out 
at the proper time, and they are perfectly independent of each 
other in all of their movements. The consequence of this 
arrangement is, that the steam valve may open, steam flow into 
the cylinder, the valve suddenly shut and chop the steam off 
short, the piston move forward in its stroke by the expansion of 
the confined steam, and finally, be let out by the opening of the 
exhaust valve, which has all the time stood ready for the dis- 
charge. Here we have a regular expansion engine. We can cut 
the steam off as early in the stroke as we desire, and hence, have 
any degree of expansion we desire. And we can do this without 
interfering with the exhaust valves. It is found, in practice, 
that an engine cutting off at about one-fifth of its stroke and 
expanding the other four-fifths, will yield the fairest practical 
economy. 

AUTOMATIC CUT-OFF ENGINES. 

In order that those not posted may understand what is meant by 
the term " Automatic Cut-off Engines," we will have to go back a 
step. Take, for instance, a full-stroke engine. It ought to be 
well understood how the ordinary governor does its work. Sup- 
pose, for instance, that there is no governor, and that we regulate 
the speed of the engine by having a man stand at the throttle-valve 
all the time. If the engine runs too fast, he shuts the throttle- 
valve a little. This makes the steam pipe so small that the steam 
cannot flow fast enough to keep the pressure up, and consequently, 



340 HANDBOOK ON ENGINEERING. 

the speed goes down. If the engine runs too slow, he opens the 
throttle- valve and lets the steam flow free, so as to maintain 
higher pressure. Thus it will be seen that the man at the throttle 
regulates the engine by altering the pressure with which the steam 
acts upon the engine. An ordinary engine governor is simply a 
man at the throttle. When the engine runs too fast the balls fly 
out, the governor valve shuts a little and the pressure of steam 
entering the engine is reduced, and so on through all the 
changes continually taking place. All steam engines, in which 
the regulation of steam is effected by means of a governor operat- 
ing upon a throttle, are called throttling engines. They operate 
by reducing the pressure of the steam admitted to the engine, and 
thereby taking so much of the vitality out of the steam. It is 
entirely the wrong way to do it. After once spending our 
money to get up pressure in the boiler, we should make the 
greatest possible use of that pressure, so long as we are taking 
the steam from the boiler. It is, therefore, desirable that 
the full boiler pressure should be admitted to our cylinder ; 
and the question arises as to how we shall be able to regulate 
the speed if we do not tinker with this pressure. The Automatic 
Engine regulates the speed by the simple act of altering the point 
of cut-off. If the engine is cutting off at one-fifth stroke, we get 
a power equal to the incoming force of steam for one-fifth of the 
stroke, and the expansion of the steam for the other four-fifths of 
the stroke. If the engine runs too slow we cut the steam off a 
little later and thereby increase the average pressure during the 
expansion. The Automatic Engine, then, is an engine, which cuts 
off the steam at an earlier point in the stroke, if the engine runs 
too fast, and cuts it off at a later point if it runs too slow. It is 
the duty of the governor to say just when the steam valve should 
close and not let any more steam into the cylinder. In the Cor- 
liss Engine the steam valves open wide at the beginning of the - 
stroke and let full boiler pressure smack in against the piston. 



HANDBOOK ON ENGINEERING. 341 

After the piston has advanced to, say one-fifth of its stroke, the 
valve shuts up as quick as a flash and the expansion begins. If 
the engine starts too slow, the governor will hold the steam valve 
open a trifle longer, but will not interfere with its full opening at 
the beginning of the stroke, or with its flash-like closing when 
the cut-off is to take place. During all these operations of the 
governor and the admission valves, the exhaust valves are let 
entirely alone, and they continue their work unchanged. It will 
thus be seen that the expansion engine makes provision for the 
utmost economy in the use of steam, and with the automatic fea- 
ture added to it, provides that this economy shall not be sacrificed 
for the purpose of regulating the speed. 

THE GARDNER SPRING GOVERNORS. 

Construction* — Two balls are rigidly connected to the upper 
ends of two flat, tapering, steel springs — the lower ends of the 
springs being secured to a revolving sleeve which receives rotation 
through mitre gears ; links connect the balls to an upper revolv- 
ing sleeve, which is free to move perpendicularly. 

The valve stem passes up through a hollow standard upon which 
the sleeves revolve, and is furnished with a suitable bearing in the 
upper sleeve ; the closing movement of the valve is upward, and 
is obtained in the following manner : The balls at the free ends of 
the springs furnish the centrifugal force and the springs are the 
main centripetal agency (gravity is not employed). As the balls 
fly outward, under the centrifugal influence, they move in a curved 
horizontal path which may be described as an arc, modified by a 
radius of changing length — the radius being represented by the 
length and position of the springs ; the links represent a radius 
of lesser length, while the sleeve to which the lower ends of the 
links are pivoted, being free to rise and fall, nullifies the effect of 
the links in determining the arc in which the balls travel. As the 



342 



HANDBOOK ON ENGINEERING. 



balls move outward in their peculiar path, the sleeve is drawn up- 
ward by the links, and, as the balls move inward, the sleeve is 
pushed downward. The change of speed is obtained by increas- 




THE GARDNER STANDARD GOVERNOR— CLASS "A" 

WITH AUTOMATIC SAFETY STOP AND SPEEDER. 



ing or decreasing the centripetal resistance, and accomplished by 
the action of a spiral spring pivoted against the lever, and by 
means of a shaft and arm against the valve-stem in the direction 
to open the valve ; a thumb-screw is used to adjust the compres- 



HANDBOOK ON ENGINEERING. 343 

sion. A convenient Sawyer's lever is attached to the shaft, and 
a reliable automatic safety stop is furnished when desired. 

The cut on the preceding page represents the Gardner Standard 
Governor, Class "A." 

This is a Gravity Governor, having an Automatic Safety Stop 
and Speeder. It is made in sizes from 11 inches to 16 in., 
and is especially adapted to the larger type of stationary engines. 
In action, the centrifugal force of the pendulous balls is opposed 
by the resistance of a weighted lever, the speed being varied by 
the position of the weight. The Automatic Safety Stop is very 
simple in construction and reliable in action. It is accomplished 
by allowing a slight oscillation of the shaft bearing, which is sup- 
ported between centers and held in position by the pull of the 
belt ; a projection at the lower part of the shaft bearing supports 
the fulcrum of the speed lever. If the belt breaks or slips off 
the pulley, the support of the fulcrum is forced back, so as to 
allow the fulcrum to drop and instantly close the valve. The 
valve is not affected by steam current and both valve and seats 
are made of special composition, that effectually resists wear 
and the cutting action of the steam. The workmanship is of the 
highest class, all parts being made by the duplicate system, with 
special machinery. 

The cut on the following page represents Class "B" Gov- 
ernor — a combination of the gravity and spring actions. 

They are made in sizes from f to 10 inches inclusive, and are 
adapted to all styles of engines. They are provided with Speeder 
and Sawyer's >Lever, but are not automatic. In the Class " B " 
Governor the centrifugal force of the pendulous balls operates 
against the resistance of a coiled steel spring, inclosed within a 
case and pivoted on the speed lever by means of a screw ; the 
amount of compression of the spring can be changed so as to give 
a wide range of speed. A continuation of the Speed Lever makes 
a convenient Sawyer's hand lever, which controls the valve by 



344 



HANDBOOK ON ENGINEERING. 



means of a cord. Sizes J to li in., inclusive, have an adjustable 
frame, which can be set at any desired angle in relation to the 




THE GARDNER STANDARD GOVERNOR — CLASS "B.' 



valve chamber. The valve and chamber are the same as used on 
Class " A " Governor, and they are made with the same care and 
style of workmanship. 



HANDBOOK ON ENGINEERING. 



345 



CHAPTER XIV. 



A FEW REHARKS ON THE INDICATOR. 

The steam-engine indicator is an instrument designed to show 
the steam pressure in the cylinder at all points in the stroke. It 
consists primarily, of a piston of known area capable of moving 
in a cylinder and resisted by a coil spring of known strength. 
To this piston is attached, by means of suitable piston rod and 
levers, a pencil capable of tracing a line corresponding to the 
motion of the indicator piston. This line is traced on a paper 
slip attached to the drum of the indicator, which drum is con- 
nected to some moving part of the engine in such away as to have 
a back and forward movement, coincident with the steam piston 
of the engine. 





By referring to the above selected view of an indicator, which 
is generally recognized as the best known, the construction will be 
readily understood.- 



346 HANDBOOK ON ENGINEERING. 

THE USE OF THE STEAn ENGINE INDICATOR IN SETTING 
VALVES AND THE INVESTIGATION OF SOME OF THE DE= 
FECTS BROUGHT OUT BY THE INDICATOR CARDS. 

The steam-en gine indicator lias come into such general use 
that to-day there are but few men running engines who are not 
familiar with its construction and manner of attachment to en- 
gines, and the method of calculating horse-power from cards. 
The indicator is attached to pipes tapped into the cylinder heads, 
or into the barrel of the cylinder opposite the counterbore, beyond 
the travel of the piston rings. The indicator consists of a cylin- 
der with piston and compression spring and a drum attached to a 
coiled spring, used for returning the same. The pressure of steam 
on the piston of the indicator compresses the spring above it. 
The motion of the piston is carried by a piston-rod to a pencil 
motion, which multiplies the motion of the spring some five or six 
times. The springs are marked 20, 40, 80, etc. This meaning ' 
that 80 lbs. pressure per square inch on the indicator piston 
(or whatever the spring may be marked) will cause the pencil 
at the end of the pencil-arm to move an inch. The pencil marks 
on paper, which is fastened on a drum. This drum is moved by 
the cross-head of the engine, through some form of reducing 
motion, such as pantograph, lazy-tongs, brumbo pulley, etc. To 
obtain the horse-power, we first need the mean pressure equiva- 
lent to the variable pressure on the card. This is most easily 
found by dividing the area of the card by the length, giving the 
height of a rectangular card of equivalent area, and then multi- 
plying this height by the scale of the spring. The mean effective 
pressure per square inch on the piston, times the area of the pis- 
ton in square inches, times the speed of the piston in feet per 
minute, divided by 33,000, gives the horse-power. If there is a 
loop at either end of the card, the area of this loop is to be sub- 
tracted from the larger area before finding the mean height of 



HANDBOOK ON ENGINEERING. 347 

the card, since such a loop represents work opposed to the work- 
ing side of the piston. In getting areas by means of a planimeter, 
no attention need be given to the loops. By following the lines 
in order, as drawn by the indicator pencil, the loops will be sub- 
tracted from the main card, for if the main body of the card is 
traced in a right-handed rotation, the loops will be traced in a 
left-handed rotation. 

DIAGRAM ANALYSIS. 

Figs* \ and 2 are from throttling engines ; the former repre- 
senting good performances for that class of engine, and the latter, 




Fig. 1. 

in some respects which the engineer will readily recognize, bad 
performances. 



348 HANDBOOK ON ENGINEERING. 

Figs, 3, 4, and 5, are from automatics; Fig. 3 representing 
what is now considered rather too light a load for best practical 
economy ; Fig. 4 about the best load, and Fig. 5 is from a con- 
densing engine. 

Line A B is the induction line, and B C the steam line ; both 
together representing the whole time of admission. 

C is about the point of cut-off, as nearly as can be determined 
by inspection. It is mostly anticipated by a partial fall of pres- 
sure due to the progressive closure of the valve. 

The usual method is, to locate it about where the line changes 
its direction of curvature. 

C D is the expansion curve. D is the point of exhaust. 

D E is the exhaust line, which begins near the end of the stroke 
and terminates at the end of the stroke, or, at latest, before the 
piston has moved any considerable distance on its return stroke. 

The principal defect of Fig. 2 is, that this line occupies nearly 
all the return stroke. E F is the back pressure line, which, in 
non-condensing engines, should be coincident with, or but little 
above, atmospheric pressure. In Fig. 5 it is below the atmos- 
pheric line to the extent of the vacuum obtained in the cylinder. 
Some authorities would call it the vacuum line in Fig. 5 but that 
name properly belongs to a line representing a perfect vacuum. 

F is the point of exhaust closure (slightly anticipated by rise 
of pressure) and F A the compression curve, which, joining the 
admission line at A, completes the diagram proper, forming a 
closed figure. 

G G is the atmospheric line traced when the piston of the indi- 
cator is subject to atmospheric pressure, above and below alike. 
Some pull the cord by hand when tracing it, to make it longer 
than the diagram. // // is the vacuum line, which, when re- 
quired, is located by measurement such a distance below the 
atmospheric line as to represent the atmospheric pressure at the 
time and place, as nearly as can be ascertained. The mean 



HANDBOOK ON ENGINEERING. 349 

atmospheric pressure at the sea level is 14.7 pounds. For higher 
altitudes, the corresponding mean pressure may be found by 
multiplying the altitude by .00053, and subtracting the product 
from 14.7. When a barometer can be consulted, its reading in 
inches multiplied by .49 will give the pressure in pounds. 




Fig. 2. 

/ is the clearance line, representing by its distance from the 
nearest point of the end of the diagram at the admission end, as 
compared with the whole length, the whole volume of clearance 
known to be present. Its use is mainly to assist in constructing 
a theoretical expansion curve by which to test the accuracy of the 
actual one. 

Calculating mean effective pressure* — Since the simplification 
and popularization of the planimeter, no engineer who has occa- 



350 



HANDBOOK ON ENGINEERING. 



sion to compute the " indicated horse-power " (IHP) of engines 
should be without one ; for, if properly handled, the results 




Fm. 3. 



obtained by them are more accurate and more quickly obtained 
than by any other process. The diagram is pinned to a smooth 
board covered with a sheet of smooth paper, the pivot of the leg 
pressed into the board at a point which will allow the tracing point 
to be moved around the outline of the diagram without forming 
unnecessarily extreme angles between the two legs, and a slight 
indentation made in the line at some point convenient for begin- 
ning and ending ; for it is vitally important that the beginning and 
ending shall be at exactly the same point. The reading of the 
wheel is taken, or it is placed at zero, and the tracing point is 



HANDBOOK ON ENGINEERING. 



351 



passed carefully around the diagram, following the lines as closely 
as possible, moving right-handed, like the hands of a watch. The 
reading obtained (by finding the difference between the two, if 
the wheel has not been placed at zero) is the area of the diagram 
in square inches, which, multiplied by the scale of the diagram, 
and divided by its length in inches, gives the mean effective 
pressure. 

The process of finding the mean effective pressure by 
ordinates. — Divide the diagram into 10 equal parts as shown by 
the full lines in Fig. 4 : but I wish to call attention to a frequent 
mistake, viz.. 




Fig. 4. 



making all the spaces equal. The end ones should be half the 
width of the others, since the ordinates stand for the centers of 



352 



HANDBOOK ON ENGINEERING. 



equal spaces. Ten is the most convenient and usual number of 
ordinates, though more would give more accurate results. The 
aggregate length of all the ordinates (most conveniently measured 
consecutively on a strip of paper) divided by their number, and 
multiplied by the scale of diagram, will give the mean effective 




Fig. 5. 



pressure. A quick way of making a close approximation to the 
mean effective pressure of a diagram is, to draw line a b, Fig. 6, 
touching at a. and so that space d will equal in area spaces c and 
e, taken together, as nearly as can be estimated by the eye. 
Then a measure,/, taken at the middle, will be the mean effective 
pressure. With a little practice, verifying the results with the 
planimeter, the ability can soon be acquired to make estimates in 



HANDBOOK ON ENGINEERING. 



353 



this way with only a fraction of a pound of error with diagrams 
representing some degree of load. With very high initial pres- 
sure and early cut-off, it is not so available. 




/ 



Fig. 6. 

The indicated horse-power. — IHP is found by multiplying 
together the area of the piston (minus half the area of the piston- 
rod section, when great accuracy is desired), the mean effective 
pressure and the travel of the piston in feet per minute, and 
dividing the product by 33,000. It is sometimes convenient to 
know the HP constant of an engine, which is the HP for one 
revolution at one pound mean effective pressure. This multiplied 
by the mean effective pressure, and by its number of revolutions 
per minute, gives the IHP. 



THEORETICAL CURVE. 

Testing expansion curves* — It is customary to assume that 
steam, in expanding, is governed by what is known as Mariotte's 
law, according to which its volume and pressure are inversely pro- 



354 



HANDBOOK ON ENGINEERING. 



portional to each other. Thus, if a cubic toot of steam at, say, 
100 pounds pressure be expanded to 2 cubic feet, its pressure 
will fall to 50 pounds, and proportionately for all other degrees 
of expansion. The pressures named are t; total pressures ; " that 
is, they are reckoned from a perfect vacuum. A theoretic ex- 
pansion curve which will conform to the above theory may be 




Fig. 7. 



traced by the following method : Referring to F 4 ^. 7, having 
drawn the clearance and vacuum lines as before explained, draw 
any convenient number of vertical lines, 1, 2, 3, 4, 5, etc., at 
equal distances apart, beginning with the clearance line and num- 
ber them as shown. Decide at what point in the expansion curve 



HANDBOOK ON ENGINEERING 



355 



of the diagram you wish the theoretic curve to coincide with it. 
Suppose you choose line 10, ou which you find the indicated pres- 
sure to be 25 pounds. Multiply this pressure by the number of 
the line (10) and divide the product (250) by the numbers of 
each of the other lines in succession. The quotients will be the 
pressures to beset off in the lines. Thus, 250 divided by 9 gives 
27.7, the pressure on line 9; and so for ail the others. The 
same curve may also be traced by several geometric methods, one 
of which is as follows, referring to Fig. 8 : — 




Fig. 8. 



Having drawn the clearance and vacuum lines as before, 
select the desired point of coincidence, as «, from which draw the 
perpendicular a A. Draw A B at any convenient height above or 
near the top of the diagram, and parallel to the vacuum line D C. 
From A draw A C and from a draw a b parallel to D C. and from 



356 HANDBOOK ON ENGINEERING. 

its intersection with A B, erect the perpendicular be, locating the 
theoretical point of cut-off on A B. From any convenient num- 
ber of points in A B (which may be located without measurement) 
as E, F, G, H, draw lines to C, and also drop perpendiculars E e, 
F f, Gg\ Hh, etc. From the intersection of E C with b c, draw a 
horizontal to e, and the same for each of the other lines F C, 
G C, H C; establishing points e,/, g, h, in the desired curve. 
Any desired number of points may be found in the same way. 
But this curve does not correctly represent the expansion of 
steam. It would do so if the steam during expansion remained 
or was maintained at a uniform temperature ; hence, it is called 
the isothermal curve, or curve of same temperature. But, in fact, 
steam and all other elastic fluids fall in temperature during expan- 
sion, and rise during compression ; and this change of temperature 
augments the change of pressure slightly ; so that if, as before 
assumed, a cubic foot of steam at 100 pounds total pressure be 
expanded to two cubic feet, the temperature will fall from nearly 
328° to about 278°, and the pressure instead of falling to fifty 
pounds, will fall a trifle below 48 pounds. A curve in which the 
pressure due to the combined effects of volume and resulting 
temperature is represented, is called the adiabatic curve, or curve 
of no transmission ; since, if no heat is transmitted to or from the 
fluid during change of volume, its sensible temperature will 
change according to a fixed ratio, which will be the same for the 
same fluid in all cases. I need not attempt to give any of the 
usual methods of tracing the adiabatic curve, since the isothermal 
curve is the one generally used for that purpose. And while it is 
incorrect in that it does not show enough change or pressure for a 
given change of volume, the great majority of actual diagrams are 
still more incorrect in the same direction ; so that when a diagram 
conforms to it as closely as the one used in these illustrations, it 
is considered a remarkably good one. A sufficiently close 
approximation to the adiabatic curve to enable the non-profes- 



HANDBOOK ON ENGINEERING. 357 

sional engineer to form an idea of the difference between the two, 
may be produced by the following process : Taking a similar 
diagram to those used for the foregoing illustrations, we fix on a 
point A near the terminal, where the total pressure is 25 pounds. 
As before, this point is chosen in order that the two curves may 
coincide at that point. Any other point might have been chosen 
for the point of coincidence ; but a point in that vicinity is generally 
chosen so that the result will show the amount of power that 
should be obtained from the existing terminal. This point is 3.3 
inches from the clearance line, and the volume of 25 pounds is 
996 ; that is, steam at that pressure has 996 times the bulk of 
water. Now, if we divide the distance of A from the clearance 
line by 996, and multiply the quotient by each of the volumes of 
the other pressures indicated by similar lines, the products will be 
the respective lengths of the lines measured from the clearance 
line, the desired curve passing through their other ends. Thus, 
the quotient of the first, or 25-pound pressure line divided by 
996 is .003313; this multiplied by 726, the volume of 25-pound 
pressure, gives 2.4, the length of the 25-pound pressure line ; and 
so on for all the rest. 

Fig* 9 shows a card taken from a Corliss engine, running at a 
speed of about ninety revolutions per minute. On account of the 
slow speed and the quick 
admission obtained by this 
form of valve gear, but lit- 
tle compression is needed. 
For high speed engines, 
there is much more com- 
pression. At high speeds, 

the expansion line of the " -— ■ . " ■ ^ - 

indicator card, instead of &• 

being a smooth curve like that shown in Fig. 9, is often : 

line, due to oscillations of the spring in the indicator. 




358 



HANDBOOK ON ENGINEERING. 




Fio-. 10. 



Fig, 10 represents what is called a stroke card. The indicator 

shows us the pressure on 
one side of the piston for 
a revolution. When we 
calculate the horse-power 
from a card, we are as- 
suming that the back pres- 
sure and compression 
line on «the other side of 
the piston are the same as 
shown on the card. This 
may or may not be the case. In calculating the total horse-power 
for the two ends of the cylinder, any error from this cause affect- 
ing the calculation for one end of the cylinder, will be nearly 
balanced by an opposite error in the calculations for the other end, 
so that the final result is practically correct. If it were not for 
the piston-rod making the area of one side of the piston smaller 
than on the other, there would be absolutely no error arising 
from this. The stroke card shows the pressure on opposite 
sides of the piston at all points of the stroke. The difference 
between the lines at any point is the effective push per square 
inch. This card is constructed by using the steam and expan- 
sion lines of the card from one end, and the back pressure 
and compression lines for the same stroke, from the card taken 
on the other end. In constructing diagram for very accurate 
work, the ratio of the areas of the two sides of the piston have 
to be considered ; the pressure above the atmosphere for one 
side being multiplied by this ratio. It will be seen that up to 
the point of cut-off, the difference of pressure, or effective pres- 
sure, is nearly constant ; this difference grows less, due to the 
drop along the expansion curve, till at the point where the 
two lines cross, the pressure on the two sides balances. Be- 
yond this point, the pressure exerted to hold the piston back 



HANDBOOK ON ENGINEERING. 



359 



is greater than that exerted to push it ahead. The energy stored in 
the fly-wheel during the first part of the stroke is given out here 
near the end of the stroke to help the engine over the dead point. 

STEAfl CHEST CARDS. 

By attaching" one indicator to the steam chest of an engine, 
and another to one end of the cylinder, it can be seen 



ports 



whether the pipes and 

sloping steam line on an indicator 

small a steam pipe, or too 

small steam ports, or to 

both of these combined. 

This does not apply, of 

course, to engines using 

throttling governors. 

Fig* i i shows the effect 
of too small steam pipe. 
When steam is admitted 
to the cylinder, there is a 
drop in pressure in the 



are of sufficient size. A 
card may be due to too 




Fig. 11. 



Steam Chest on Forward 
Stroke. 

chest. This drop becomes greater in amount as the speed of the 

piston increases. At cut- 
off, the flow of steam into 
the cylinder stops, then 
the pressure in the chest 
reaches boiler pressure. 
If there is no great drop 
in the line on the steam 
chest card, and a consid- 
erable drop in the steam 
line of the card, it would 
mean that the ports are 
case is shown bv Fig. 12. 




Fig. 12. Steam Chest Card on 
Forward Stroke. 

too small. Such 



360 



HANDBOOK ON ENGINEERING. 




Fig. 13. Steam Chest Card on 
Forward Stroke. 



If there is a drop in 
the chest line up to cut- 
off, and a still greater 
drop in the steam line 
of the card, it would 
indicate that both the 
steam ports and the 
steam pipe were too 
small. Fig. 13 shows 
such a case. 




ECCENTRIC OUT OF PLACE. 

Fig's* 14, 15, \6 f and 17, show cards taken from a Corliss En- 
gine having the eccentric out of adjustment. Similar cards would 
be obtained from any en- 
gine having all the valves 
moved by one eccentric. 
The plain slide valve and 
the locomotive, especially 
in full gear, would give 
similar cards for the same 
derangements of eccen- 
tric. 

Fig* 14 was taken with 
the eccentric a trifle less 
than 90° ahead of the crank, or about 20° behind where it belongs 
on this particular engine. 

Fig* 15 shows the eccentric moved too far ahead of the crank. 

By comparison with Fig. 9, it will be seen that moving the 
eccentric back makes all the events of the stroke, such as admis- 
sion, release and compression and cut-off, in the case of engines 
without automatic cut-off governor, come later ; while moving 
the eccentric ahead brings these events earlier. 




Figs. 14 and 15. 



HANDBOOK ON ENGINEERING. 



361 




Figs. 16 and 17. 



Figs. J 6 and 17 are similar to Figs. 14 and 15, the only differ- 
ence being that eccentric is moved a greater distance out of place. 

In Fig. \ 6 the admission 
is very late. Release does 
not occur until after the 
piston has started on the 
return stroke, the steam, 
until released, being com- 
pressed back along the ex- 
pansion curve. This com- 
pression is always a trifle 
below the expansion line, 
due to the fact that some of the steam has condensed in the 
interval between the end of the stroke and the release. 

Fig. \ 7 shows too much compression and too early a release. 
Steam is compressed above boiler pressure in the cylinder, when 
the valve lifts and the steam escapes into the chest. 

Cards like Figs. 14 and 15 are very common. 

ECCENTRIC CARDS. 

As small distances near the ends of the indicator cards repre- 
sent a large angular motion of the crank, the events occurring at 
the ends of the card are so squeezed together that it is hard to 
tell from the card just what any peculiarity in the lines may be 
due to. The eccentric rod working the valves of the engine will 
be moving at its greatest speed when the crank is near the centers 
and the piston near the ends of the stroke ; since the eccentric is 
about 90° ahead of the crank. If the motion of the indicator 
drum is taken from the eccentric rod instead of the cross-head, the 
card will be changed in shape, compression and release coming 
near the middle of the card, and being spread out over consider- 
able length, the cut-off, expansion and back pressure lines coming 
near the ends of the card. 



362 



HANDBOOK ON ENGINEERING. 



Fig* J8 gives a steam card drawn, assuming that the expansion 
and compression lines are hyperbolic. The eccentric card for this 

had been plotted, and cor- 
responding points marked 
with the same letters. The 





Fig. 18. 



Fig. 19. 



compression curve, extending from F to 'A, is a double curve. 
Admission occurs at A, cut-off at B, release at C, and compres- 
sion at F. 

Figs. J 9 and 20 show cards taken from an engine having tight 
valves and a tight piston. Corresponding points on the two cards 

are lettered the same. For a 
cut-off later than half stroke, 
the steam line on the eccen- 
tric card doubles on itself, as 
shown in Figs. 21 and 22. 

The peculiar bend shown 
by the dotted lines on corn- 




Fig. 20. 

pression curve of the steam card, 
Fig. 18, is developed on the 
eccentric card into a well marked 
flat place. Evidently this rep- 
resents a loss of pressure at this 
point, which may be attributed 
to one or more of three causes : 
first, leakage by the piston ; 
second, leakage by the exhaust valves; third, a rapid condensa- 



Fiff. 21. 



HANDBOOK ON ENGINEERING. 



363 




Fig. 22. 



tion of steam. If a leakage, it is probable that there is steaui 
blowing by all through the stroke. 
Near the end of the stroke the pis- 
ton is moving at so slow a rate that 
the leakage overbalances the com- 
pression. It frequently happens 
that the pressure drops off at the 
end of compression, making the 
upper end of the compression line 

resemble an inverted letter U. If the leakage is by the piston, 
it will appear or may be made to appear near release, as will be 
explained later. The effect of compressing steam is to dry it, 
or, if dry already, to superheat it. While it may be possible in 
some cases for some of the drop here to be due to condensation, 
in the majority of cases leakage is the trouble. 

Fig. 23 shows the effect of a bad leakage by the piston. This 
leakage is made evident by the appearance of the upper end of 

the compression curve 
and by the increase in 
pressure along the expan- 
sion line just before re- 
lease. By referring to 
the stroke card, it will be 
seen that near this point 
the pressures on the oppo- 
site side of the piston are 
the greater, so that the leakage is now into the side on which the 
card is being taken. Unless compression on one side comes 
earlier than release on the other side, this method would fail. 
In most engines the valves are set so that compression does 
come earlier, and all four valve engines can be easily set so 
as to delay release on one end, and to hasten compression on the 
other end. In the case of a Corliss engine, this means simply 




Fiff. 23. 



364 HANDBOOK ON ENGINEERING' 

the changing the length of the rods leading from the wrist plate 
to the valve arm. This change can be made with the engine run- 
ning. It is possible that a card like Fig. 23 might be obtained 
from a four-valve engine having a leaky steam valve on one end 
and a leaky exhaust valve on the other end. 

Fig"* 24 represents the head end and the crank end cards 
taken from a plain slide valve engine. The valve has equal 
steam laps and equal exhaust laps. The only trouble in this case 




Fig. 24. 

is that the valve spindle is too short. Shortening the valve spin- 
dle decreases the outside lap of the valve and increases the inside 
lap for the head end side, and. increases the outside lap and de- 
creases the inside lap for the crank end side. As will be seen by 
the cards, the head end has the cut-off lengthened, the release 
delayed, and the compression hastened; the crank-end has the 
cut-off shortened, the release hastened, and the compression de- 
layed. If the valve spindle were too long the cards shown would 
be interchanged, the crank end card being the one marked head 
end. 

THE STEAM ENGINE INDICATOR. 

Benefits derived and information ascertained from its use* — 
The benefits derived, and the information ascertained from the 
use of the steam-engine indicator are varied and important. 



HANDBOOK ON ENGINEERING. 365 

" The office of the indicator is to furnish a diagram of the 
action of the steam in the cylinder of an engine during one or 
more revolutions of the crank, from which is deduced the follow- 
ing data : Initial pressure in cylinder ; piston stroke to cut-off ; 
reduction of pressure from commencement of piston stroke to cut- 
off ; piston stroke to release ; terminal pressure ; gain in econ- 
omy due expansion ; counter pressure, if engine is worked, 
non-condensing ; vacuum as realized in the cylinder, if engine is 
worked condensing ; piston stroke to exhaust closure, usually 
reckoned from zero point of stroke ; value of cushion ; effect of 
lead and mean effective pressure on the piston during complete 
stroke. The indicator diagram, when taken in connection with 
the mean area and stroke of piston and revolution of crank 
for a given length of time, enables us to ascertain the power de- 
veloped by engine ; and when taken in connection with the mean 
area of piston, piston speed and ratio of cylinder clearance, 
enables us to ascertain the steam accounted for by the engine. 

i; The mean power developed by engine compared with the 
steam delivered by boilers, furnishes cost of power in steam, 
and when compared with the coal, furnishes cost of the power in 
fuel. 

" The diagram also enables us to determine with precision the 
size of steam and exhaust ports necessary, under given conditions, 
to equalize the valve functions ; to measure the loss of pressure 
between boiler and engine ; to measure the loss of vacuum be- 
tween condenser and cylinder ; to determine leaks into and out 
of the cylinder ; to determine relative effects of jacketed and 
un jacketed cylinders ; and to determine effects of expansion in 
one cylinder, and in two or more cylinders." 

TO TAKE A DIAGRAM. 

Connecting-cord* — The indicator should be connected to the. 
engine cross-head by as short a length of cord as possible. Cord 



366 HANDBOOK ON ENGINEERING. 

having very little stretch, such as accompanies the instrument, 
should be used ; and in cases of very long lengths, wire should 
be used. The short piece of cord connected with the indicator is 
furnished with a hook; and at the end of the cord, connected 
with the engine, a running loop can be made by means of the 
small plate sent with each instrument; by which the cord can be 
adjusted to the proper length, and lengthened or shortened as 
required. 

Selecting- a spring". — It is hot advisable to use too light a 
spring for the pressure. Two inches are sufficient for the height 
of diagram, and the instrument will be less liable to damage if 
the proper spring is used. The gauge pressure divided by 2 
will give the scale of spring to give a diagram two inches high at 
that pressure. 

To attach a card* — This may be done in a variety of ways, 
either by passing the ends of it under the spring clips, or by 
folding one end under the left clip, and bringing the other end 
around under the right; but, whatever method is applied, care 
should be taken to have the card rest smoothly and evenly on the 
paper drum. Now attach the cord from the reducing motion to 
the engine ; but be certain the cord is of the proper length, so as 
to prevent paper drum from striking the inner stop in drum 
movement on either end of the stroke. 

Tension of drum spring* — The tension of the drum spring 
should be adjusted according to the speed of the engine ; in- 
creasing for quick running, and loosening for slower speeds. 

The steam should not be allowed into the indicator until it has 
first been allowed to escape through the relief on side of cock, to 
see if is clean and dry. If clean and dry, allow it into the indi- 
cator, and allow piston to play up and down freely. 

Before taking- diagram, turn the handle of cock to a horizontal 
position, so as to shut off steam from piston, and apply pencil to 
the paper to take the atmospheric line. 



HANDBOOK ON ENGINEERING. 



367 



In applying pencil to the card, always use the horn-handle 
screw, to regulate pressure of pencil upon paper to produce as 
fine a line as possible. After the atmospheric line is taken, turn 
on steam, and press the pencil against card during one revolution. 

When the load is varying, and the average horse-power re- 
quired, it is better to allow the pencil to remain during a number 
of revolutions, and to take the mean effective pressure from the 
card. 



Fig. 25. 
Fig. 25 was taken from a Russell engine 13"x20", running 
205 revolutions per minute, boiler pressure 98 lbs., scale of indi- 
cator 60 lbs. Duty, electric lighting. 



After sufficient number of diagrams have been taken, remove 
the piston, spring, etc., from the indicator, while it is still upon 
the cylinder ; allow the steam to blow for a moment through the 
indicator cylinder; and then turn attention to the piston, spring, 
and all movable parts, which may be thoroughly wiped, oiled and 
cleaned. Particular attention should be paid to the springs, as 
their accuracy will be impaired if they are allowed to rust ; and 
great care should be exercised that no grit or substance be intro- 
duced to cut the cylinder, or scratch the piston. Be careful 



368 HANDBOOK ON ENGINEERING. 

always not to bend the steel bars or rods. The heat of the steam 
blown through the cjdinder of the indicator will be found to have 
dried it perfectly, and the instrument may be put together with 
the assurance that it is all ready for use when required. Other 
items of precaution should be borne in mind. Any engineer 
can easily repeat this operation without further instruction. 



Fig. 26. 

Fig. 26 was taken from a Russell engine 16"x24", running 
157 revolutions per minute, boiler pressure 70 lbs., scale of indi- 
cator 40 lbs. Duty, flouring mill. 





Frjction Indication. Full Load- Indication. 

Harrisburg Ideal Simple Single Valve Engine. 
Fig. 27. Fig. 28. 



HANDBOOK ON ENGINEERING. 



369 




Graduated Load 
Indication. 




Extreme Load Variation 
Indication. 



Harrisburg -Ideal Simple Single Valve Engine.) 
Fig. 29. Fig. 30. 





High pressure Indication. Low pressure Indication. 

Harrisburg Ideal Compound Single Valve Engine. 



Fig. 31. 



Fig. 32. 





Friction Indication. Full Load Indication. 

Harrisburg Standard Simple Single Valve Engine. 



Fig. 33. 



Fig. 34. 



370 HANDBOOK ON ENGINEERING. 





Friction Indication. Full Load Indication. 

Harrisburg Standard Simple Four-Valve Engine. 
Fig. 35. Fig. 36. 





High Pressure Indication. Low Pressure Indication*, 

Harrisburg Standard Compound Four-Valve Engine. 
Fig. 37. Fig. 38. 

Figs* 27, 28, 21), 30, 31, 32, 33, 34, 35, 36, 37 unci 38 are 
cards taken from the Harrisburg Ideal and Standard Engines. 
An engineer will see from these cards the kind of card he should 
get from a high speed engine of this class. 

Fig* 39 i- s from a Frick Corliss Engine, driving a Frick Com- 
pressor : — 

Steam Cylinder iy"x 28". 

Steam 1)5 lbs. 

Revs 58 

Cond. Press. 164 lbs. 

Back Press 27 lbs. 



HANDBOOK ON ENGINEERING. 



371 




V_ 



„ine, 19" x 28". 
Steam, 95 lbs. 
Revs. 58 lbs. 
Cond. Press., 1M lbs. 
Back Press. . 27 lbs-. 



Fig. 39. 



INDICATOR DIAGRAMS FROM 50-TON "ECLIPSE' 
MACHINE. 



R. Hand Pump^ 
12$" s 28". 
Scale. 120 If*. 




Fig. 40. 
Fig, 40 is R. Hand Pump. 1.21" x 28". Scale, 120 lbs. 



m 



HANDBOOK ON ENGINEERING. 



L.-Hand Pump. 
12J" x 28". 
Scale, 120 lbs. 



Fig. 41. 
Fig. 4t is L. Hand Pump. 27£" x 28". Scale, 120 lbs. 



~\ 



Engine, SO" x 36" 
Steam, 75 #>s. 
/2eys. 44 

<?otw2. Press., 162 /to, 
^a^ Press., 10 Ms. 



Fig. 42. 

Figs* 42. 43 and 44 are diagrams from a 100-ton " Eclipse 
Machine." 



HANDBOOK ON ENGINEERING. 



373 



iNDICATOR DIAGRAMS FROM 100-TON "ECLIPSE." 
MACHINE. 



R. Hand Pump* 
17" x 36". 
Scale, 80 lbs, 




Fig. 43. 



L. Rand Piemp^ 
17" x 36". 
Scale. 80 l&S 




Fig. 44. 



374 



HANDBOOK ON ENGINEERING. 




HANDBOOK ON ENGINEERING. 375 

It will be interesting to note that when the eccentric is simply 
moved forward or backward around the shaft by the action of the 
governor, all the events of the stroke — admission, release, cut-off 
and compression — will be hastened or retarded together ; but if 
the eccentric be so designed that the governor will shift it across 
the shaft instead of around it, the admission and release will be 
effected differently, and in the opposite direction from the cut-off 
and compression. If, for example, the cut-off is made to occur 
earlier in the stroke, the compression will occur earlier also, but 
the admission and release will occur later instead of earlier. By 
combining the two movements of the eccentric and having the 
governor move it partly around and partly across the shaft, it is 
possible to keep the admission and release nearly constant, while 
the cut-off and compression vary. This result is attained to a 
certain extent in the best single-valve engines. Besides these two 
types, there are numerous other styles of engines in which the 
point of cut-off is varied automatically. Instead of a shaft gov- 
ernor with a shifting eccentric, a weighted pendulum governor is 
sometimes employed to operate the link, or radius rod of some 
one of the various link motions. Sometimes there are separate 
admission and exhaust valves, the former being under the con- 
trol of a shaft governor, and the latter operated by a fixed eccen- 
tric, so that the points of admission and cut-off only are varied, 
while the points of release and compression, which depend upon 
the exhaust valve, remain fixed. There are a great many modifi- 
cations of the Corliss engine, as originally constructed by 
Geo. H. Corliss, and there are many engines which, while not re- 
sembling the Corliss engine, have some arrangement whereby the 
cut-off valves are tripped. 

On pages 374 and 376 is a collection of diagrams which 
illustrate very nicely the peculiarities and difference in the action 
of throttling and automatic engines. The four diagrams on 
page 374 were taken from a Ball automatic, in an electric light 



376 



HANDBOOK ON ENGINEERING. 




HANDBOOK ON ENGINEERING. 377 

station. The first diagram was taken late in the afternoon when 
the engine was started and before any load was thrown on to the 
machine, and the three succeeding cards were taken at intervals 
later in the evening as the number of lights increased and the 
load became heavier. Two or three important points are to be 
noticed in connection with these diagrams. First, the initial 
pressure of the steam at the point of admission is very nearly the 
same in all four cards, the slight variations being due chiefly to a 
variation in the boiler pressure. Second, the length of the cut-off 
increases with the load. The compression also becomes later as 
the cut-off lengthens, and while there is also a change in the points 
of admission and release, it is not as marked as the changes in cut- 
off and compression, for reasons that have already been explained. 

Taking- the cards on page 376, we have four excellent examples 
of the action of a throttling engine. These cards are from a 
Dickson engine, taken at the same station and under the same 
conditions as the Ball engine cards, with the exception that in 
this case both head and crank-end diagrams were taken on the 
same cards, while only the head end diagrams from the Ball 
engine are shown. The two sets of diagrams are well adapted 
for comparison, because both engines are of the single-valve type, 
with the valve moved by one eccentric. 

The points to be noted are, first, that the points of cut-off are 
the same, namely at about | stroke, in all the throttling cards, 
and second, that the power of the engine is increased by the action 
of the governor in opening a throttle valve wider, allowing steam 
to enter the cylinder at higher pressure. 

It was stated at the outset that automatic regulation is the 
most approved method for regulating the speed of steam engines 
at the present time. It is generally believed and it is probably 
true, that automatic engines give better economy than throttling 
engines and that they regulate a little more closely. It will 
readily be seen that when the governor of the automatic engine 



37$ HANDBOOK OX ENGINEERING. 

changes position, it measures out just the quantity of steam that 
will be required to keep the engine within the speed limits during 
the following stroke. The effect of this regulation, moreover, is 
felt at one point in the stroke only — the point of cut-off — so that 
any change in the governor up to the time when the piston nears 
the point of cut-off will produce an immediate change in the 
quantity of steam admitted. In the throttling engine, on the 
other hand, the regulation is effected during the whole stroke up to 
the point of cut-off, and the full effect of any change of the gov- 
ernor cannot be felt until the next stroke. With regard to the 
relative economy of the two types, it should be kept in mind that 
the throttling engine is generally of cheap construction, has large 
clearance, a single, unbalanced slide-valve that does duty for both 
entering and exhaust steam and aside from the throttling feature, 
is inferior to the average automatic engine. It is reasonable to 
suppose, therefore, that at least a part of the large steam con- 
sumption generally attributed to the throttling engine is due to 
its inferior design and construction and not to its method of 
governing. 

For example, take the case of the Ball and the Dickson engines, 
from which I have shown cards. They both have a single slide- 
valve, but the former runs at higher speed than the latter and its 
valve is balanced, so that for these reasons it would be expected 
to be a little more economical. We should not expect, however, 
that a test would show any decided superiority that could be 
attributed to the method of governing. If we were to compare 
the average throttling engine with the most approved type of 
automatic engine, like the Corliss, we should find that the effi- 
ciency of the latter was much higher. The gain, however, would 
be due to a large extent to the small clearance spaces, separate 
steam and exhaust valves, and other important features of the 
Corliss engine, rather than to its automatic cut-off. It is not 
the purpose to discuss here why these features give improved 



HANDBOOK ON ENGINP^ERING. 379 

economy over the single valve, but simply call attention to the 
fact that they exert an important influence. The exact influence 
which the throttling or automatic features exert apart from the 
general constructive features of the engine is hard to determine. 
It is known that high-pressure steam is more economical to use 
than low pressure steam and the automatic engine, which pre- 
serves nearly the boiler pressure up to the point of cat-off, gains 
on this account. On the other hand, it is known that the most 
economical point of cut-off for a non-condensing engine is about 
one-third stroke, and when it becomes very much less than this 
there is a serious drop in the economy. A very short cut-off 
with high-pressure steam produces so great a variation in the 
temperature during one stroke of the piston that the cylinder 
condensation becomes excessive. For very light loads, therefore, 
it would be better to throttle the steam than to shorten the cut-off. 
It is necessary for all engines to have a reserve of power and 
hence the cut-off of throttling engines must come late in the 
stroke. If it were early in the stroke, there would not be enough 
reserve power with the reduction in the pressure of the steam that 
is necessary with this type. The late cut-off produces poor 
economy when the load is heavy, because there will then be a 
high terminal pressure, and a large amount of heat, corresponding 
to this pressure, will be thrown away. A throttling engine there- 
fore, may be expected to do better at light loads than at heavy 
ones, and in fact, may do a little better at light loads than the 
automatic engine. If a throttling engine could be run so as not 
to vary much from its most economical load, and could be de- 
signed to have the good features of the best automatic engines, 
with the cut-off at an earlier period in the stroke, it would prob- 
ably be nearly or quite as well as the automatic engine. Under 
the conditions that the} T have to run, however, the automatic engine 
will keep the lead, although, as explained above, its superiority 
is not due entirely to the automatic feature. 



380 HANDBOOK OF ENGINEERING. 



CHAPTER XV. 

Engineers over the country have been discussing whether or 
not more steam is used when an engine is made to run faster without 
changing either the cut-off or the back pressure. Some, strange as 
it may seem, have actuallj r held to the opinion that, since the cut- 
off is not changed, no more steam is used, and hence, if it were 
possible to make an engine run faster without changing the cut-off, 
it would be doing more work than before without any increase in 
the consumption of steam. Of course, this is wrong. The speed 
of an engine, almost any engine, may easily be increased without 
changing the cut-off, and when this is done, the engine will do 
more work and will use more steam. It is utterly impossible to 
get something for nothing out of a steam-engine, or out of any 
engine or appliance. The only way in which a steam-engine can 
be made to do more work without using more steam is to increase 
its efficiency. And when everything else is kept the same and the 
speed only of an engine increased, the efficiency is very slightly 
increased. The condensation is decreased with an increase of 
speed, but the decrease would be so slight for most cases that it 
would hardly be worth considering. When an engine is cutting 
off at a certain part of the stroke, it uses at every stroke a cer- 
tain weight of steam which depends upon the initial pressure of 
the steam, clearance volume of the engine and the point of cut- 
off. If the engine makes 400 strokes per minute (200 revolu- 
tions, if a double acting engine) the weight of steam used will be 



HANDBOOK ON ENGINEERING. 381 

400 times the weight used in one stroke ; but if the engine be 
made to make 500 strokes per minute, the weight of steam used 
per minute will be, neglecting the small difference in condensa-' 
tion, 500 times the weight used in one stroke. 

HOW TO INCREASE THE SPEED, OR INCREASE THE POWER 
OF A CORLISS ENGINE. 

There are three ways in which this can be done. Take, for 
example, a 24"x48" simple Corliss engine making 70 revolu- 
tions per minute, the boiler gauge pressure 80 lbs. per square 
inch, one-quarter cut-off, or cut-off 12 inches from the beginning 
of the stroke ; the mean effective pressure, say about 42 lbs. per 
sq. in., the governor pulley on the main shaft 10 inches in diam- 
eter, the pulley on the governor shaft 7 in. in diameter, and the 
friction of engine, cylinder clearance, condensation, etc., left 
entirely out of the question. It is desired to increase the speed 
of this engine to 80 revolutions per minute, and in this manner 
increase its horse-power. 

First method* — Regardless of piston rod, the area of the pis- 
ton is 452.4 square inches, nearly. The piston speed of this 
engine is 560 feet per minute, and its horse-power 322, nearly. 

452.4x42x560 
Thus: oo 00n =322. So that the horse-power of this 

engine at 70 revolutions per minute is 322, nearly, and this is 
what the manufacturer's catalogue gives. Now, in order to get 
80 revolutions per minute, take the 7-inch pulley off the governor 
shaft, and put in its place an 8-inch pulley. Thus : 70 : 80 : : 
7:8. Then, the governor balls will revolve in the same relative 
plane that they did before, and the cut-off will remain the same ; 
that is, at one-quarter, or 12 in. of the stroke. Thus, 7: 10:: 
70 : 100. And 8 : 10 : : 80 : 100. So the governor balls make 100 
revolutions per minute, both before and after making the change. 



382 HANDBOOK ON ENGINEERING. 

Now, with the engine speeded up to 80 revolutions per minute, 

we get 46 more horse-power. Thus : Piston speed equals 640 

452.4x42x640 
feet per minute. Then, s^non ~ ^ horse-power, 

nearly. And 368 minus 322 =46. Now, it would appear that 

we are getting 46 horse-power more for nothing, but such is not 

452.4 x 12x2x70 
the case. For, T^28 =439.8 + , or nearly 440 

cubic ft. of steam per minute, at 80 lbs. boiler pressure, are 

452. 4x 12x2x80 
required to develop 322 horse-power. And, r^9H 

= 502.6-f- or nearly 503 cubic ft. of steam per minute, at 80 

lbs. boiler pressure, are required to develop 368 horse-power. 

Then, 503 minus 440 = 63 cubic feet more of steam at 80 lbs. 

boiler pressure, which means more water evaporated per minute 

and more coal burned per hour. 

Second method* — Retain the same engine speed and the same 

cut-off, but increase the boiler pressure from 80 to 90 lbs. Then 

80 : 90 : : 42 : 47-^, call it 48 lbs. mean effective pressure. 

452.4x48x560 
Then, ^°non = 368 horse-power, nearly, the same as 

before, and as given in the manufacturer's catalogue. We are 

now using 440 cubic feet of steam per minute at 90 lbs. pressure, 

with an increase of 6 lbs. M. E. P. ; consequently, more coal per 

hour must be burned. 

Third method* — Retain the same boiler pressure, that is 80 

lbs., and weight the governor so as to make the balls revolve in a 

lower plane in order to give a later cut-off . Thus, 322: 368:: 

J:f. That is, the cut-off must take place at about f of the 

stroke instead of at J. Then, J: ^::42:48. That is the 

M. E. P. will be 48 lbs. per square inch with a cut-off at -| of the 

452.4 x 48 x 560 
stroke. Then, h°ooo = 368 horse-power, the same as 



HANDBOOK ON ENGINEERING. 383 

before. But, -| of 48 = 13^, or 13.71 inches nearly, so that, 

instead of cutting off at 12 inches with 80 lbs. boiler pressure, 

we are cutting off at 13.71 inches and using 63 cubic feet more 

. , _ 452.4x13.71x2x70 RnQ , 

steam per minute. Ihus, = 503, nearly. 

1 1728 

And, 503 minus 440 =63, that is, we must use 63 cubic feet 

more of steam per minute at 80 lbs. boiler pressure, in order to 

get 46 more horse-power, which means the evaporation of more 

water per minute, and the burning of more coal per hour. 



HOW TO INCREASE THE HORSE=POWER OF AN ENGINE 
HAVING A THROTTLING GOVERNOR. 

There are three ways in which this can be done, also. We 
will take, for example, a plain slide-valve engine 10x16 inches, 
making 150 revolutions per minute, with T 9 g cut-off, and M. E. P. 
say 311 lbs. per square inch, with a boiler pressure of 60 lbs. 
by gauge. The governor pulley on the main shaft 6 inches 
in diameter, and the pulley on the governor shaft 4 inches 
in diameter. The horse-power of this engine is about 30. 

Thus, 16x2 = 2| ft., and 150 x 2f =400 ft., the piston speed. 

™ 10 x 10 x. 7854x31. 5x400 OA , 

I hen, = .30 horse-power, nearly. 

33000 

It is now desired to run the engine at 180 revolutions per 
minute in order to develop 6 horse-power more. In order to 
obtain these results, the governor pulley must be enlarged, so as 
to make the governor balls revolve in the same plane at 180 revo- 
lutions per minute, that they now do at 150 revolutions. Thus, 
4:6:: 150: 225, that is, the governor balls are now making 
225 revolutions per minute. And 150: 180 ::4:4.8. Con- 
sequently, the governor pulley must be increased to 4.8 inches in 



384 HANDBOOK ON ENGINEERING. 

diameter. Then, 4.8 : 6 : : 180 : 225, that is, the governor balls, 
after the change, making the same number of revolutions as 
before. At 180 revolutions per minute, the piston speed is 480 

feet per minute. Thus, 16x2 = 2-|. And, 180x24 = 480. 
12 3 3 

;~ 78.54x31.5x480 on , , T , . ,. 

Ihen, = 36 horse-power, nearly. It might 

33000 

seem from the above that we are getting 6 horse-power more for 

nothing ; but such is not the case. For, cutting off at T 9 ^ is 

equivalent to cutting off at 9 inches of the stroke. 

_, 78.54x9x2x150 1SiQ ,<.■-, , 

Then, — 123 cubic ft., nearly. 

1728 

A , 78.54x9x2x180 ^ Ar . .. ' j \ , A -, 

And, , =147 cubic feet, nearly. And, 

1728 J 

147 minus 123 = 24. So that for 6 horse-power more, we are 

using 24 cubic feet more of steam per minute, at 31.5 lbs. M. E.P., 

w T hich means more water evaporated per minute and more coal 

burned per hour. 

If trie boiler pressure may be safely increased, we can get 6 

horse-power more out of the engine without increasing its speed, 

by running the boiler pressure up to 75 lbs. by gauge. Thus 75 

lbs. boiler pressure would give about 37.8 lbs. M. E. P. with T 9 F 

cut-off. Then, 78,54 X 37,8 x40Q = 36 horse-power, nearly. 
33000 F 

In this case no change should be made in the governor, nor in 

the speed of the engine. We can also get 6 horse-power more 

out of this engine by cutting off later, say at §, in order to get 

37.8 lbs. M. E. P. But a later cut-off is not desirable, because 

it is not economical of steam, and besides, it would require a new 

valve, new eccentric, or a change in the length of a rocker arm, if 

not a change of the valve-seat, because the travel of the valve 

would have to be increased. 



HANDBOOK ON ENGINEERING. 385 

HOW TO INCREASE THE HORSE=POWER OF AN ENGINE 
HAVING A SHAFT GOVERNOR. 

Suppose it is desired to increase the speed of the engine from 250 
to 275 revolutions per minute, cutting off at J stroke. In this 
case the governor springs should be so adjusted that the throw of 
the eccentric will be the same at 275 revolutions that it was at 250 
revolutions. This will require an increased consumption of steam 
per minute at the same initial cylinder pressure as before making 
the change, consequently more fuel will be required. If the speed 
of the engine is not to be changed, an increase of the horse-power 
may be obtained by increasing the initial cylinder pressure, if the 
condition of the boiler will so permit. Or, the initial cylinder 
pressure may remain unchanged and the governor springs and 
levers so adjusted as to give a later cut-off, say at | or -^ of the 
stroke, or whatever may be required to offset the increased per- 
manent load, the speed of the engine remaining unchanged. Any 
one of the changes above described would necessitate an increased 
consumption of fuel. 

HOW TO LINE THE ENGINE WITH A SHAFT PLACED AT A 
HIGHER OR A LOWER LEVEL. 

We will suppose the latter shaft not yet in place, but to be 
represented by a line tightly drawn. From two points as far 
apart as practicable, drop plumb lines nearly, but not quite, 
touching this line. Then by these strain another line parallel 
with the first, and at the same level as the center line of 
th^ engine, and at right angles with this stretch another represent- 
ing this center line, and extend both each wa}^ to permanent walls 
on which their terminations, when finally located, should be care- 
fully marked, so they can at any time be reset. The problem is 
to get the latter line exactly at right angles with the former. 
Everything depends upon the accuracy with which this right 

25 



386 



HANDBOOK ON ENGINEERING. 



angle is determined. It is done by the method of right-angled 
triangles. There are two ways of applying this method. In the 
first, one end of a measuring line is attached to some point of 
line No. 1, and its other end is taken successively to points on 
line No. 2 on opposite sides of the intersection, as illustrated in 
the following figure, in which A B is a portion of line No. 1, and 
C D of line No. 2, the direction of which is to be determined. 
B F and B G are the same measuring line fixed at B, and applied 
to the line C I) successively at the points F and G. The dis- 




tances B F and B G being, therefore, the same, when E F is 
equal to E G, the lines A B and C D are at right angles with each 
other. In the second, application is made of the law that the square 
of the hypothenuse of a right-angle triangle is equal to the sum 
of the squares of the other two sides. Thus 3 2 -j- 4 2 = 5 2 . So if 
the above figure E B = 4,E F=S, and B F= 5, the angle at 
E is a right-angle. Any unit of measure may be used, a foot is 
generally the convenient one ; so any multiple of these numbers 
may be taken; as, for example, 6, 8 and 10. Respecting the 
comparative advantages of these two ways, the situation will often 
determine which is to be preferred. In the former, the diagonal 



HANDBOOK ON ENGINEERING. 387 

being the same line, fixed at B and brought successively to the 
points F and 6r, its length is immaterial, though generally the 
longer the better ; and the only point to be determined is the 
equality of E F and E G, which may be compared with each 
other by marks on a rod. In the latter, the proportionate 
lengths, 3, 4 and 5, or their multiples, must be exactly measured. 
It is better adapted to places where a floor is laid and the meas- 
urements can be transferred by trammels. The result should be 
verified by repeating the operation on the opposite side of the 
intersection at E, and when so verified we have, in fact, the first 
process, without the additional and unnecessary trouble of deter- 
mining the relative lengths of the lines. Care should be taken 
when a measuring line is used, to avoid errors from its elasticity, 
Ou this account, a rod is often employed. Points on the lines 
are best marked by tying on a white thread. 

HOW TO LINE THE ENGINE WITH A SHAFT TO WHICH IT IS 
TO BE COUPLED DIRECT. 

In this case, it is supposed that the engine- bed and the bear- 
ings for the shaft are already approximately in position. They 
are leveled by a parallel straight edge and a spirit level. To line 
them horizontally, a line must be run through the whole series of 
bearings and continued to a permanent wall at each end, and its 
terminating points, when determined, carefully marked, as already 
directed. A piece of wood is tightly set in each end of each 
bearing and the surfaces of these are painted white or chalked. 
Then the middle of each piece being found by the compasses, two 
fine lines are drawn across it, equally distant from the middle, and 
having between them a space a little wider than the thickness of 
the line. This being then strained, nearly touching those blocks, 
or, if long, having its sag supported by them, the two marks on 
each block must be seen, one on each side of the line, with the 
line of white between. 



388 HANDBOOK ON ENGINEERING. 

HOW TO SET A SLIDE VALVE IN A HURRY. 

Open your cylinder cocks ; then open the throttle slightly, so 
as to admit a small amount of steam to the steam-chest. Roll 
your eccentric forward in the direction the engine runs, until 
steam escapes from the cylinder cock at the end where the valve 
should begin to open. Now screw your eccentric fast to the 
shaft. Roll your crank tojthe next center and ascertain if steam 
escapes at the same point, at the opposite end of the cylinder. 
If so, ring your bell and go ahead. You are all right and can run 
until an opportunity occurs to you to open your steam-chest and 
examine your valve. 

DO YOU DO THESE THINGS? 

A writer in a contemporary asks and answers the following 
pertinent questions : — 

Do you take a squirt-can in one hand and project a stream of 
oil as far as you can throw it, in order to save going to the oil 
hole itself ? 

If you do, don't do it any more; willful waste is downright 
robbery. 

Do you use an oil can at all for oiling, except on emergency, or 
for the moment ? 

If you do, don't do it any more, for much better lubrications 
can be had by automatic apparatus. 

Do you keep an old tin coffee pot full of suet on the steam- 
chest, and every time you have nothing else to do, pour a dipper- 
ful into the steam-chest? 

If you do, stop it and get a sight-feed cup, which will save 
you the labor of slushing the cylinder and save the cylinder and 
valve-seats, the piston and follower, and all other places touched 
by the grease. 



HANDBOOK ON ENGINEERING. 



389 



Do you feed the boiler until the water is out of sight iu the 
glass, then shut off the feed, put in a big lire and sit down in 
a dark corner with a four-horse brier pipe and smoke, until you 
happen to think that maybe the water is low ? 

If you do these things you should notify the coroner that some 
day his services will be needed, but it is better to cease the prac- 
tice mentioned before the coroner comes. 

Do you stop leaks about the boiler as fast as they occur, or do 
you wait until the places sound like a snake's den before you stir? 

If you do, you waste heat, which is the same word as money, 
only differently spelled. Every jet of hot water leaking from a 
steam boiler is just so much money thrown away, and if it was 
your money you would be bankrupt in a short time, in some 
boiler rooms. 

Do you take a screw wrench and yank away at a bolt or nut 
under steam pressure? 

If you do, there will come a time, sooner or later, when you 
will do so once too often, and either kill yourself or some one else. 
Bolts and nuts are liable to strip or break if tampered with under 
pressure, and they never tell any one beforehand when they are 
going to do it, 

Do you attempt to stop pounding in the engine by laying for 
the crank-pin as it comes round , and trying to hit the key once in 
a while ? 

If you do, ask the strap and neck of the connecting-rod how 
he likes it, when you don't hit the key and do hit the oil cup? 

Do you pack the piston by taking it out of the cylinder, lay- 
ing it on the floor, setting out the rings, and then when the piston 
will not go into the cylinder, try to batter it in with a four-foot 
stick of cord wood? 

If you do, you should reform, and pack the j^iston in the 
cylinder where it belongs, being sure to get it central by meas- 
uring from the lathe center in the end of the piston rod. 



390 



HANDBOOK ON ENGINEERING. 



Do you put a new turn of packing on top of the old, hard- 
burned stuff when the piston rod leaks steam ? 

If you do, you will have a scored piston rod and broken gland 
bolts some day. Packing under heat and pressure gets so hard 
that it cuts like a file when left in the stuffing box, and as one 
begins to leak all the old stuff should be pulled out and new put 
in its place. 



Fig. 1. 



Fig. 2. 




THE TRAVEL OF A SIDE VALVE. 

The travel of a slide valve is found as follows : The maximum 
port opening at the head end, plus the maximum port opening at 
the crank end, plus the lap at the head end, plus the lap at the 
crank end. Therefore — , 1|" -J- 1|" -|- J" -f- f" =4J-"? the re- 
quired travel of valve. Incidentally, it may be well to mention 
that the travel of a valve may also be obtained from the eccentric, 
by subtracting the thin part of the eccentric from the thick 
part as per Fig. 1, or again, by taking twice the distance between 
the center of rotation and center of the eccentric. This distance 
on the eccentric is the end valve travel, and is termed the " throw " 
of the eccentric. In the above question, the travel may also be 



HANDBOOK ON ENGINEERING. 



391 



found by the aid of the diagram, Fig. 2, which is explained as 
follows: From the center A, with a radius of J inch (lap), 
describe a circle BCD. From any point in the circumference, 
say B, lay off the distance B E equal to the maximum port open- 
ing, If" ; from the center A, with a radius A E, describe the 
circle E F O; the diameter of the circle E F G is equal to the 
travel of the valve, which is 4i". Let the readers try this with 
another set of figures, to prove the correctness of the diagram. 

LOSS OF HEAT FROM UNCOVERED STEAM PIPES. 

The following table shows the loss of heat through naked steam 
pipes, wrought iron, of standard sizes. The best covering for a 
steam pipe is hair felt from one to two inches thick, depending on 
the diameter of the pipe, say one inch thick for pipe from 1 to 4 
inches in diameter, and two inches or more for larger pipes. 
Such covering will save at least 96 per cent. Cheaper coverings 
will save from 75 to 90 per cent. The chief value of the table is 
as an aid in estimating the saving that can be made by covering 
the pipe. The money loss by naked pipe being known, the sav- 
ing can be estimated and the cost of the covering will decide its 
value as an investment. 

TABLE OF MONEY LOSS FROM 100 FEET OF NAKED STEAM PIPE, FOR 
ONE YEAR OF 3000 WORKING HOURS. 



Ml • 


STEAM PRESSURES. 




50 


60 


70 


80 


90 


100 


^=5o.S 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


1 


|13.15 


$13.70 


.$14.20 


.$14.66 


$15.08 


$15.47 


H 


16.58 


17.29 


17.92 


18.49 


19.02 


19.51 


H 


-18.98 


19.78 


20.51 


21.17 


21.77 


22.33 


2 


23.72 


24.73 


25.63 


26.45 


27.21 


27.91 


2h 


28.72 


29.94 


31.03 


32.03 


32.94 


33.79 


3 


34.97 


36.45 


37.78 


38.99 


40.10 


41.14 


4 


44.96 


46.86 


48.57 


50.13 


51.56 


52.89 


5 


55.57 


57.92 


60.04 


61.96 


63.73 


65.38 


6 


66.27 


69.08 


71.60 


73.89 


76.01 


77.96 



392 HANDBOOK ON ENGINEERING. 



RULES AND PROBLEMS APPERTAINING TO THE STEAM 
ENGINE. 

To find the H. P. of a simple. non-condensing engine: — 

Rule* — -Multiply the net area of the piston in square inches, 
by the mean effective pressure in pounds per square inch, and by 
the velocity of the piston in feet per minute, and divide the last 
product by 33,000. The quotient will be the gross H. P. Sub- 
tract from this from ten to twenty per cent for friction in the 
engine itself, and the remainder will be the delivered H. P. 

Example. — The area of the piston is 500 sqr. ins. Half the 
area of the piston-rod is 5 sqr. ins. The M. E. P. is 50 lbs. 
per sqr. in. The stroke is 3 feet, and the revolutions per minute 
125. The friction is 10 per cent. What is the delivered H. P.. 
of the engine? Ans. 506.25 H. P. 

Operation* — 3 ft. x2=6 ft. twice the stroke. 

Then, 500 — 5 =495 sqr ins. net area of piston. 

And, 125 X 6 = 750 ft. the piston speed per minute. 

And, 495X50X750 g ^, 
33,000 

Then, 562.5 X -90 == 506.25. The delivered H. P. 

For a condensing engine: — Add the vacuum to the M. E. P. 
and proceed as above. 

The M. E. P. is the average pressure in the cylinder, less the 
back pressure. 

To find the H. P. of a compound noncondensing engine : — 

The usual method of calculating the H. P. of a multiple cyl- 
inder engine is to assume that all the work is done in the low 
pressure cylinder alone, and that such a M. E. P. is obtained in 
that cylinder as will give the same H. P. as is given by the .whole 
engine. 

Rule* — Find the ratio of areas of the high and low pressure 
cylinders, — when of the same stroke, as they usually are,— and 



HANDBOOK ON ENGINEERING. 393 

multiply it by the number of expansions in the high pressure 
cylinder, for the total number of expansions in both cylinders. 
Find the hyperbolic logarithm corresponding to this result and 
add 1 to it, and divide the sum by the total number of expan- 
sions. Multiply this result by the absolute steam pressure, and 
subtract the back pressure. Subtract again the loss in pressure 
between cylinders, and the remainder will be the M. E. P. Then 
multiply the net area of the low pressure cylinder by this M. E. P. 
and by the piston speed in feet per minute and divide by 33,000. 
Deduct the friction in the engine itself and the remainder will be 
the delivered H. P. 

Example. — Given a tandem compound engine with cylinders 
20" and 32" diameter, and 4 feet stroke, making 75 revolutions 
per minute, boiler gauge pressure 125 lbs. per sqr. in., J cut-off 
in high pressure cylinder, back pressure 15 J lbs. per sqr. in., 
drop in pressure between cylinders 15 per cent, and friction in 
engine 10 per cent. What is the H. P. delivered of this engine? 
Ans. 338.4 II. P. 

Operation. — Neglecting the areas of the piston rods, we 
have : — 

20 X 20 X .7854 = 314.16 sqr. ins. area of high pressure 
cylinder. 

And, 32 X 32 X .7854 = 804.2 sqr. ins. area of low pressure 
cylinder. 

Then, 804.2 H- 314.16 =2.56 =the ratio between cylinders. 

And, 2.56 X 4 = 10.24 = the total number of expansions. 
The hyperbolic logarithm of 10.24 = 2.328. (See table on p. 397.) 

And, 1 + 2.328 = 3.328. 

Then, 3.328 -f- 10.24-= .325., 

Also, 125 + 15 = 140 lbs., the absolute pressure. 

And, .325 X 140 =45.5 lbs., forward pressure. 

And, 45.5 — 15.25 = 30.25 lbs., the M. E. P. 



394 HANDBOOK ON ENGINEERING. 

And, 30.25 X .85 = 25.7 lbs. = the M. E. P. less the 

" drop." 

™ 804.2 X 25.7 X« X 75 a ,- fl „ „ , 

Ihen, _ _ — _ = 376 H. P. nearly. 

33,000 J 

And, 376 X .90 = 338.4 H. P. delivered. 

For a compound condensing engine, proceed as above, except 
that the condenser pressure, due to impaired vacuum, only should 
be subtracted from the forward pressure. 

To find the linear expansion of a wrought-iron pipe or bar : — 

Rule. — Multiply the length of the pipe or bar in inches by 
the increase in temperature,- and by the constant number .0007, 
and divide the last product by 100. 

Example. — Given a 6 inch wrought-iron pipe 75 feet long. 
Steam pressure 150 lbs. by gauge. Temperature of pipe when 
put up 60 degs. Fah. What is its linear expansion? Ans. 
2 ins. nearly. 

Operation. — The diameter of the pipe cuts no figure. 

Then, 150 lbs. pressure = 366 degs. 

And, 366 — 60 = 306 degs. 

Also, 75 X 12 = 900 inches length of pipe. 

Than 306 X 900 X - 0007 1 Q078 ■ 1 

I hen, _ _ = 1.9278 inch. 

For copper, use the constant number .0009 ; for brass, use 
.00107 ; for fire-brick, use .0003, and proceed as above. 

To find the proper diameter of steam pipe for an engine : — 

The velocity of steam flowing to an engine should not exceed 
6,000 feet per minute. 

Rule. — Multiply the area of thepiston in square inches by the 
piston speed in feet per minute, and divide by 6,000 ; and divide 
again by .7854, and extract the square root for the diameter of the 
pipe and take the nearest commercial size. 

Example. — Given a 20" X 48" Corliss engine making 72 revo- 
lutions per minute. What should be the diameter of its steam 
pipe? Ans. 6 inches. 



HANDBOOK ON ENGINEERING. 395 



Operation*— 20 X 20 X -7854 =314.16 sqr. ins. 

48" X 2 X 72 
And, —576 ft. the piston speed. 

. , 314.16 X576 Qn 1f , 

And. — =30.15. 

6,000 



Then, . 30,15 = 6.1". Take6"pipe. 
' \.7854 FF 

To find the water consumption of a steam engine : — 

The most reliable method for determining this, is to make an 
evaporation test, that is, to measure the water fed to the boiler in 
a given time and delivered to the engine in the form of steam. 
But as this method entails considerable trouble and expense, it is 
frequently figured from indicator diagrams. This plan, however, 
does not insure correct results, because the amount of water ac- 
counted for by the indicator is considerably less than it should be 
owing to cylinder condensation and leakage, so that it might be 
possible that only 80 per cent of the water passing through the 
cylinder would be accounted for by the indicator. But the cal- 
culation, used in connection with an evaporation test, will reveal 
the extent of the losses caused by cylinder condensation and 
leakage, by deducting the amount of water found by computation 
from the amount of water fed to the boiler while making an 
evaporation test. 

Rule* — Divide the constant number 859,375 by the M. E. P. 
of any indicator card, and divide this quotient by the volume of 
its total terminal pressure, the result will be the theoretical con- 
sumption in pounds of water per horse power per hour. 

The constant number 859,375 is found as follows: — 

Compute the size of an engine that will give just one horse- 
power at one pound M. E. P. per square inch, thus: 

Area of piston equals 412.5 sqr. inches. 

Stroke equals 4 feet, and revolutions per minute equal 10. 



396 



HANDBOOK ON ENGINEERING. 



Then, the piston speed is (4 X 2 X 10) 80 feet per minute. 

a 412.5 X 1X80 

Aud ' 33,000 ^ 

To find how much water it would take to run this engine one 
hour, allowing 62 \ lbs. to the cubic foot of water, proceed as 
follows : — 

Twice the stroke equals 90 inches. 
412.5 X 96 



Then, 



1728 



equals 22.91666 cubic feet for one revo- 



lution. 

And, 22.91666 X 10 equals 229.1666 cubic feet for 10 revolu- 
tions, or for one, minute. 

Then, 229.1666 X 60 X 62J equals 859,375 lbs. of water used 
per hour. 




Fig. 1 is not an actual indicator card, but answers to illustrate 
the rule. 

A A is the atmospheric line, and from A to A is the whole 
stroke. 

VV is the vacuum line. 

Points (a) and (6) are equally distant from the vacuum line. 
The point (a) is taken at or very near the point of release. 



HANDBOOK ON ENGINEERING. 



• 397 



Example. — From the indicator card Fig. 1 compute the water 
consumption, the M. E. P. being 37.6 lbs. per square inch, the 
scale of spring used in the indicator being 40, the distance from 
point (a) to point (6) being 3.03 inches, the stroke AA being 
3.45 inches, and the pressure at point (a) being 25 lbs. per sqr. 
inch absolute. Ans. 20.14 lbs. 

Operation*— 859, 375 -f- 37.6 — 22,855.7. 

Now, the absolute pressure at point (a) is 25 lbs., and steam 
tables give 996 as the volume of steam at this pressure, that is, 
steam at this pressure has 996 times the bulk of the water from 
which it was generated. 

Then, 22,855.7 -=- 996 = 22.94 lbs. of water. But as the 
period of consumption is represented by (&) (a), AA being the 
whole stroke, the following correction is required: The distance 
from point (a) to point (6) is 3.03 ins. Then, 22.94 X 3.03 = 
69.5080. And the whole stroke or length of line AA is 3.45 
ins. 

Then, 69.5080-^-3.45 = 20.14 lbs, of water per indicated 
horse power per hour. 

TABLE OF HYPERBOLIC LOGARITHMS. 



NO. 


LOGARITHM. 


NO. 


LOGARITHM. 


NO. 


LOGARITHM. 


1.25 


.22314 


5. 


1.60943 


9.5 


2.25129 


1.5 


.40546 


5.25 


1.65822 


10. 


2.30258 


1.75 


.55961 


5.5 


1.70474 


10.24 


2.328 


2. 


■ .69314 


5.75 


1.74917 


11. 


2.39789 


2.25 


.81093 


6. 


1.79175 


12. 


2.48490 


2.5 


.91629 


6.25 


1.83258 


13. 


2.56494 


2.75 


1.01160 


6.5 


1.87180 


14. 


2.63905 


3. 


1.09861 


6.75 


1.90954 


15. 


2.70805 


3.25 


1.17865 


7. 


1.94591 


16. 


2.77258 


3.5 


1.25276 


7.25 


1.98100 


17. 


2.83421 


3.75 


1.32175 


7.5 


2.01490 


18. 


2.89037 


4. 


1.38629 


7.75 


2.04769 


19. 


2.94443 


4.25 


1.44691 


8. 


2.07944 


20. 


2.99573 


4.5 


1.50507 


8.5 


2.14006 


21. 


3.04452 


4.75 


1.55814 


9. 


2.19722 


22. 


3.09104 



398 HANDBOOK ON ENGINEERING. 

THE STEAM BOILER. 

CHAPTER XVI. 

THE FORCE OF STEAM AND WHERE IT COMES FROH. 

If water be heated it will expand somewhat, and will finally 
burst forth into vapor. The vapor will expand enormously, and 
naturally occupy more space than the water from which it is 
formed. A cubic inch of water will make a cubic foot of steam ; 
that is, the water has been expanded by heat to seventeen hundred 
times its original bulk. The steam is very elastic ; the water was 
not. When we say that a cubic inch of water will form a cubic 
foot of steam, we mean that it will do so when the steam is allowed 
to rise naturally from the water without any confinement; If the 
steam is confined, as it would be in a boiler, it could not expand, 
and consequently would not. If the steam is allowed to rise into the 
atmosphere from an open vessel, the pressure of the steam would be 
precisely the same as the pressure of the atmosphere, that pressure 
being about fifteen pounds to the square inch. An ordinary steam 
gauge only takes notice of the pressure above the atmospheric 
pressure. When the hand of the steam gauge stands at zero, it 
indicates that there is no pressure above the ordinary pressure of 
the atmosphere. An ordinary steam gauge not connected with 
anything has the atmosphere acting upon it in both directions, the 
same as the atmosphere acts upon everything when it can reach 
both sides. If the air be pumped out of the steam gauge, the 
atmosphere will then act upon one side, and the hand will move 
backward until it stands at fifteen points less than nothing. In 
this condition the steam gauge indicates the absolute zero of 
pressure. If now the air be allowed to re-enter where it was 
pumped out, it will begin to exert its pressure upon the steam 



HANDBOOK ON ENGINEERING. 399 

gauge, and the hand will move forward ; when the full air 
pressure is on, the gauge hand will stand at its usual zero. 
To go into this matter in order that it may be understood 
that the real pressure of steam is always fifteen pounds greater 
than ordinary steam gauges indicate. In all of the finer cal- 
culations relating to the action of steam, its total pressure must 
be known, and this total pressure is to be counted from the 
absolute zero. The real pressure of steam is always the steam 
gauge pressure, plus iifeeen pounds. When a steam gauge shows 
fifty pounds, the steam really has a pressure of sixty-five pounds. 
The fifteen pounds of this pressure is nullified by the atmospheric 
pressure, and the steam gauge shows us our useful pressure. As 
before stated, a cubic inch of water will make a cubic foot of 
steam at atmospheric pressure ; that is, fifteen pounds to the 
square inch, abolute pressure, or zero by the steam gauge. If 
this cubic inch of water was made into steam in a boiler holding 
just a cubic foot, the steam gauge would show zero. If the boiler 
was only large enough to hold half a cubic foot, the steam would 
all be in the boiler, and being confined in half its natural space, 
it would have double pressure. It would have an absolute pres- 
sure of thirty pounds to the square inch, and the steam gauge 
would indicate fifteen pounds. If this steam was then allowed to 
pass into a chamber holding a cubic foot, the steam would expand 
until it filled the chamber, and its pressure would go down again 
to fifteen pounds absolute. In short, the pressure is in reverse 
proportion to the amount of space it occupies. The pressure of 
steam may be doubled by compressing the steam into 
one-half its former volume, and so on. After water is 
turned into steam, the steam may be made hotter, but 
it is not very much expanded. The pressure of steam 
is increased by forcing more steam into the space occupied. 
If a boiler contains steam at 50 lbs. pressure, we may increase 
. the pressure by adding more steam, and thus compressing all the 



400 HANDBOOK ON ENGINEERING. 

steam that the boiler contains. In the ordinary operation of a 
steam boiler, the fire turns the water into steam and the more 
steam there is made and confined, the greater the pressure will 
be. If the steam is constantly flowing out of the boiler into an 
engine, the pressure in the boiler must be kept up by continually 
making new steam to take the place of that drawn off. If we 
make steam as fast as it is drawn off, and no faster, the pressure 
will remain the same. If we make steam faster than the engine 
draws it off, the pressure will rise, and if it is drawn off faster 
than we make it, the pressure will go down. 

The pressure of the steam is due to its desire to expand into a 
larger body, and it acts outwardly in every direction against 
everything upon which it presses. If we crowd 600 cu. ft. of 
steam in a boiler, which will only hold 100 cu. ft., the steam will 
be held compressed into one-sixth its natural bulk, and will thus 
have a pressure of 90 lbs., and the steam gauge will show 75 lbs. 
If a hole 1 in. square be cut in the boiler, and a weight of 75 lbs. 
be laid over the hole, the steam will just lift the weight. If the 
atmospheric pressure could be removed from one sq. in. of the 
top of the weight, the steam would then be capable of lifting a 
90 lb. weight. The force which this steam will exert to lift a 
weight, or any similar thing against which it acts, will equal the 
pressure per square inch multiplied by the number of square 
inches which the steam acts upon. It will thus be readily under- 
stood that if we lead a pipe from the boiler and lit a piston in the 
pipe, the steam will tend to force this piston out of the pipe. 

THE ENERGY STORED IN STEAM BOILERS. 

A steam boiler is not only an apparatus by means of which the 
potential energy of chemical affinity is rendered actual, and avail- 
able, but it is also a storage reservoir, or a magazine, in which a 
quantity of such energy is temporarily held ; and this quantity, 



HANDBOOK ON ENGINEERING. 401 

always enormous, is directly proportional to the weight of water 
and of steam which the boiler at the time contains. The energy 
of gunpowder is somewhat variable, but a cubic foot of heated 
water under a pressure of 60 or 70 lbs. per square inch, has about 
the same energy as one pound of gunpowder ; at a low red heat, 
it has about forty times this amount of energy. 

The letters B. T. U. are the initial letters of the words British 
Thermal Unit, and are used as abbreviations of those words. 
The British Thermal Unit is the unit of heat used in this country 
and England, and may be said to be the amount of heat required 
to raise the temperature of one pound of pure water from 60 to 61 
degrees Fahr. It is often necessary to distinguish between 
B. T. U. used in this country and the French thermal unit used in 
France and most of the countries of Europe. The French ther- 
mal unit is called the calorie, and is the heat required to raise the 
temperature of one kilogram of water one degree centigrade. 

Safety at high pressure depends entirely upon the design, 
material, and workmanship, and it is a question that may be re- 
garded as settled long since, that a steam boiler properly con- 
structed and designed for a working pressure of 150 pounds is as 
safe as a properly constructed boiler designed for eighty pounds, 
with the chances in favor of the high pressure, for the reason that 
less care is taken in selecting boilers for the ordinary pressure, as 
anything in the shape of a boiler is regarded, by careless people, 
as good enough for the lower pressures, with which they have 
become so familiar as to become almost too careless. 

SPECIAL HIGH PRESSURE BOILERS. 

The extending use of compound steam engines, which make 
necessary the employment of high steam pressures, calls for steam 
boilers specially designed to successfully operate under working 
pressures ranging from 100 to 160 pounds. These boilers must 
be safe and economical and of such construction as to afford 

26 



402 HANDBOOK ON ENGINEERING. 

access for examination and repair, moderate in first cost an I 
maintenance and of simplest possible form. Fortunately, tiie 
controlling conditions are not difficult to meet, and there are sev- 
eral well-tried and approved types of steam boilers from winch to 
make your selection, choice being governed by the space at dis- 
posal, arrangement of plant, kind of fuel and other circum- 
stances. 

TYPES OF BOILERS. 

Four types that are very succesfully used, and they represent 
good practice for high pressure work, being respectively the Hori- 
zontal Tubular, and Vertical Fire Box Tubular Boilers. The Fire 
Box Locomotive Tubular Boiler may safely be added to this list 
and gives most excellent satisfaction. 

THE WATER TUBE BOILER. 

Steam boilers must be designed with reference to the pres- 
sure of steam to be carried , and when so designed and constructed 
are quite as safe at one pressure as another, preference being- 
given to the type that is simplest in form and the least liable to 
destruction, not so much by reason of the pressure carried as by 
failure to provide for the strains of expansion and contraction 
within itself. 

HORSE POWER OF BOILERS. 

In determining the proper size or evaporating capacity of a 
boiler to supply steam for a given purpose, it is necessary to con- 
sider the number of pounds of dry steam actually required per 
hour at the stated pressure. The standard horse power rating 
for any steam boiler is 34| pounds of water evaporated (made into 
steam) from feed water at 212° per hour. The total pounds 
steam required for your purpose per hour on this basis divided by 
34^ will give the standard boiler horse power required. Manu- 



HANDBOOK ON ENGINEERING. 403 

faeturers of steam boilers sometimes rate the horse power of their 
boilers by so many square feet of heating surface per horse power ; 
8 to 15 sq. ft. of heating surface, they figure, equals one horse 
power. This rating does not represent the actual capacity of the 
steam boiler, the only safe guide being the evaporative perform- 
ance in pounds of steam from water at 212° to steam at 212°. 
Some boilers will evaporate this with 8 sq. ft., some requiring 
from 15 to 18 sq. ft., hence, the absurdity of rating horse power 
of boilers of unlike construction by the square feet of heating- 
surface. But as the practice is an old one in the case of the 
well-known tubular boiler, so deservedly popular and used more 
than any other kind, good practice is to allow approximately as 
follows : — 



Allow for each Horse Power - 



Steam for Heating, etc. 



15 sq. ft. heating surface. 



For Plain Throttle Engine, ... 15 " " " 

For Simple Corliss Engine ... 12 " " " 

For Compound Corliss Condensing .10 " " " 

Hence, a boiler for heating purposes or furnishing steam for — 

Plain Slide engine with 1,500 sq. ft. surface, equals . 100 H. P. 
For Simple Corliss Engine, same boiler " . 125 H. P. 

For Compound Engine 4t . 150 H. P. 

The best method is to compare boilers with their evaporative 
efficiency and not by heating surface. 

The following is an approximate consumption of steam per 
indicated horse power per hour for engine : — 

Plain Slide Engine 60 to 70 pounds. 

High Speed Automatic Engine 30 to 50 " 

Simple Corliss Engine 25 to 35 " 

Compound Corliss Engine 15 to 20 " 

Triple Expansion Engine 13 to 17 " 



404 HANDBOOK ON ENGINEERING. 

depending upon the horse power, steam pressure, condition of 
engine, load, etc. 

Each pound of first-class steam coal consumed under a well- 
proportioned steam boiler, well managed, should evaporate 10 
pounds of steam from water 212° to steam at 212°. The average 
boiler throughout the country, with ordinary fuel and manage- 
ment, ranges from 5 to 8 pounds steam per pound of coal, and it 
would scarcely be safe to make fuel guarantees per horse power 
of engine without a counter guarantee on the part of the pur- 
chaser, when his old boiler is used, that the fuel economy is based 
on an evaporative efficiency of a given pounds water evaporated 
per pound of coal per hour of his boiler. The usual practice is 
to ignore the boiler altogether and guarantee pounds of steam 
per indicated horse power per hour used by the engine. This 
affords an exact method and is not hampered by unknown con- 
ditions and places all tests on an equal or comparative basis. 

IHE RATING OF BOILERS. 

It is considered usually advisable to assume a set of practically 
attainable conditions in average good practice, and to take the 
power so obtainable as the measure of the power of the boiler in 
commercial and engineering transactions. The unit generally 
assumed has been usually the weight of steam demanded per horse 
power per hour by a fairly good steam engine. In the time of 
Watt, one cubic foot of water per hour was thought fair ; at the 
middle of the present century, ten pounds of coal was a usual 
figure, and five pounds, commonly equivalent to about 40 lbs. of 
feed water evaporated, was allowed the best engines. After the 
introduction of the modern forms of engine, this last figure was 
reduced 25 per cent, and the most recent improvements have still 
further lessened the consumption of fuel and of steam. By general 
consent the unit has now become thirty pounds of dry steam per 



HANDBOOK ON ENGINEERING. 405 

horse power per hour, which represents the performance of non- 
condensing engines. Large engines, with condensers and com- 
pound cylinders, will do still better. A committee of the 
American Society of Mechanical Engineers recommended thirty 
pounds as the unit of boiler power, and this is now generally 
accepted. They advised that the commercial horse power be 
taken as an evaporation of 30 lbs. of water per hour from a feed 
water temperature of 100° Fahr. into steam at 70 lbs. gauge pres- 
sure, which may be considered equal to 34^ lbs. of water evapo- 
ration, that is, 34J lbs. of water evaporated from a feed water 
temperature of 212° Fahr. into steam at the same temperature. 
This standard is equal to 33,305 British thermal units per hour. 
A boiler rated at any stated power should be capable of 
developing that power with easy firing, moderate draught and 
ordinary fuel, while exhibiting good economy, and at least 
one-third more than its rated power to meet emergencies. 

WORKING CAPACITY OF BOILERS. 

The capacity or horse- power of a boiler, as rated for purposes 
of the trade, is commonly based upon the extent of heating- 
surface which it contains. The ordinary rating was for a long 
time 15 sq. ft. of surface per horse-power. At the present time 
most of the stationary boilers are sold on the basis of from 10 to 
12 sq. ft. per horse-pow r er, the power referred to being the unit 
of 30 lbs. evaporation per hour. This method of rating is arbi- 
trary, inasmuch as it is independent of any condition pertaining 
to the practical work of the boiler. The fact that 10 or 12 sq. 
ft. of surface is sold for one horse-power is no guarantee that this 
extent of surface will have a capacity of one horse-power when 
the boiler is installed and set to work. The boiler in service • 
and the boiler in the shop are two entirely different things, and 
where one passes to the other, the trade rating disappears. New 



4-0(1 HANDBOOK ON ENGINEERING. 

conditions, such as draft, grate surface, kind of fuel and man- 
agement, then take effect, and these have a controlling influence 
upon the working capacity. The working power may be found 
to be much less than the arbitrary rate, or it may be a much 
larger quantity ; all depending upon the surrounding conditions. 
I call attention to this subject, because it is important in some 
cases to have a clearer understanding as to what is the working- 
capacity of a boiler. Suppose a boiler manufacturer enters into 
an agreement to install a boiler which will have a capacity of 100 
horse-power. Suppose that on account of poor draft, low grade 
of fuel, or unfavorable surroundings, all of which are known 
beforehand, the boiler develops the power named only with the 
most careful handling. Is the working capacity, under the cir- 
cumstances, 100 horse-power? Assuredly not, for the purchaser 
could not depend upon it in ordinary running for that amount of 
power. Yet the builder may claim that he has fulfilled his 
contract. 

The former boiler test committee of the American Society of 
Mechanical Engineers established a working rate for boiler capac- 
ity which meets such cases in a definite and satisfactory manner. 
They realized that for the purpose of good work, a boiler should 
be capable of developing its capacity with a moderate draft and 
easy firing ; and that it should be capable of doing one-third more 
in cases of emergency. In other words, a boiler which is sold 
for 100 horse-power should develop 133| horse-power under con- 
ditions giving a maximum capacity. In the instance cited above, 
the boiler should have been capable of giving 100 horse-power 
with such ease that there would be a reserve of 33 J horse-power 
available when urged to this extra power. According to this 
rule, the capacity of a boiler in a working plant would be found 
by determining how much water it can evaporate under conditions 
which will give its maximum capacity ; that is, with wide open 
damper, with the maximum draft available and with the best con- 



HANDBOOK ON ENGINEERING. 407 

ditions as to the handling of the lire, and in this way ascertain 
the maximum power available under these circumstances. Hav- 
ing found this maximum quantity, the working capacity or the 
rated power would be determined by deducting from the maxi- 
mum 25 per cent. This rule, it will be seen, does not take into 
account the extent of the heating surface or the trade rating, but 
it deals solely with the capabilities of the boiler under the con- 
ditions which pertain to its work. 

CODE OF RULES FOR BOILER TESTS. 

Starting and stopping" a test* — A test should last at least 
ten hours of continuous running, and twenty-four hours whenever 
j^racticable. The conditions of the boiler and furnace in all 
respects should be, as nearly as possible, the same at the end 
as at the beginning of the test. The steam pressure should be 
the same ; the water level the same ; the fire upon the grates 
should be the same in quantity and condition ; and the walls, flues, 
etc., should be of the same temperature, To secure as near an 
approximation to exact conformity as possible in conditions of 
the fire and in the temperature of the walls and flues, the follow- 
ing method of starting and stopping a test should be adopted : — 

Standard method* — Steam being raised to the working pres- 
sure, remove rapidly all the lire from the grate, close the damper, 
clean the ash-pit, and, as quickly as possible, start a new lire with 
weighed wood and coal, noting the time of starting the test and 
the height of the water level while the water is in a quiescent 
state, just before lighting the fire. At the end of the test, re- 
move the whole fire, clean the grates and ash-pit, and note the 
water-level when the water is in a quiescent state ; record the time 
of hauling the fire as the end of the test. The water-level should 
be as nearly as possible the same as at the beginning of the test. 
If it is not the same, a correction should be made by computa- 



408 HANDBOOK ON ENGINEERING. 

tion, and not by operating pump after test is completed. It will 
generally be necessary to regulate the discharge of steam from the 
boiler tested by means of the stop-valve for a time while fires are 
being hauled at the beginning and at the end of the test, in order 
to keep the steam pressure in the boiler at those times up to the 
average during the test. 

Alternate method* — Instead of the standard method above 
described, the following may be employed where local conditions 
render it necessary : At the regular time for slicing and cleaning 
fires have them burned rather low, as is usual before cleaning, 
and then thoroughly cleaned ; note the amount of coal left on the 
grate as nearly as it can be estimated ; note the pressure of steam 
and the height of the water-level ■— which should be at the medium 
height to be carried throughout the test — at the same time ; and 
note this time as the time for starting the test. Fresh coal which 
has been weighed, should now be fired. The ash-pits should be 
thoroughly cleaned at once before starting. Before the end of the 
test the fires should be burned low, just as before the start, and 
the fires cleaned in such a manner as to leave the same amount 
of fire, and in the same condition, on the grates as on the start. 
The water-level and steam pressure should be brought to the same 
point as at the start, and the time of the ending of the test should 
be noted just before fresh coal is fired. 

DURING THE TEST. 

Keep the conditions uniform. — The boiler should be run con- 
tinuously without stopping for meal-times, or for rise or fall of 
pressure of steam due to change of demand for steam. The 
draught being adjusted to the rate of evaporation or combustion 
desired before the test is begun, it should be retained constant 
during the test by means of the damper. If the boiler is not con- 
nected to the same steam-pipe with other boilers, an extra outlet 



HANDBOOK ON ENGINEERING. 409 

for steam with valve in same should be provided, so that in case 
the pressure should rise to that at which the safety valve is set, it 
may be reduced to the desired point by opening the extra outlet, 
without checking the lire. If the boiler is connected to a main 
steam-pipe with other boilers, the safety valve on the boiler being 
tested should be set a few pounds higher than those of the other 
boilers, so that in case of a rise in the pressure the other boilers 
may blow off, and the pressure be reduced by closing their dam- 
pers, allowing the damper of the boiler being tested to remain 
open, and firing as usual. All the conditions should be kept as 
nearly uniform as possible, such as force of draught, pressure of 
steam and height of water. The time of cleaning the fires will 
depend upon the character of the fuel, the rapidity of combustion 
and the kind of grates. When very good coal is used and the 
combustion not too rapid, a ten-hour test may be run without any 
cleaning of the grates, other than-just before the beginning and 
just before the end of the test. But in case the grates have to be 
cleaned during the test, the intervals between one cleaning and 
another should be uniform. 

Keeping - the records* — The coal should be weighed and 
delivered to the firemen in equal portions, each sufficient for about 
one hour's run, and a fresh portion should not be delivered until 
the previous one has all been fired. The time required to con- 
sume each portion should be noted, the time being recorded at the 
instant of firing the first of each new portion. It is desirable that 
at the same time the amount of water fed into the boiler should 
be accurately noted and recorded, including the height of the 
water in the boiler, and the average pressure of steam and tem- 
perature of feed during the time. By thus recording the 
amount of water evaporated by successive portions of coal, the 
record of the test may be divided into several divisions, if desired 
at the end of the test, to discover the degree of uniformity of com- 
bustion, evaporation and economy at different stages of the test. 



410 HANDBOOK ON ENGINEERING. 



PRIMING TESTS. 



In all tests in which accuracy of results is important, calori- 
meter tests should be made of the percentage of moisture in the 
steam, or of the degree of superheating. At least ten such 
tests should be made during the trial of the boiler, or so many as 
to reduce the probable average error to less than one per cent, 
and the final records of the boiler tests corrected according to the 
average results of the calorimeter tests. On account of the 
difficulty of securing accuracy in these tests, the greatest care 
should be taken in the measurements of weights and temperatures. 
The thermometers should be accurate to within a tenth of one 
degree, and the scales on which the water is weighed to within 
one-hundredth of a pound. 

ANALYSES OF GASES. 

Measurement of air supply, etc, — In tests for purposes of 
scientific research, in which the determination of all the variables 
entering into the test is desired, certain observations should be 
made which are in general not necessary in tests for commercial 
purposes. These are the measurements of the air supply, the 
determination of its contained moisture, the measurement and 
analysis of the flue gases, the determination of the amount of heat 
lost by radiation, of the amount of infiltration of air through the 
setting, the direct determination by calorimeter experiments of 
the absolute heating value of the fuel, and (by condensation of 
all the steam made by the boiler) of the total heat imparted to 
the water. 

The analysis of the flue gases is an especially valuable 
method of determining the relative value of different methods of 
firing, or of different kinds of furnaces. In making these 
analyses, great care should be taken to procure average samples 



HANDBOOK ON ENGINEERING. 



411 



since the composition is apt to vary at different points of the tine, 
and the analyses should be intrusted only to a thoroughly com- 
petent chemist, who is provided with complete and accurate 
apparatus. As the determination of the other variables men- 
tioned above are not likely to be undertaken except by engineers 
of high scientific attainments, and as apparatus for making them 
is likely to be improved in the course of scientific research, it is 
not deemed advisable to include in this code any specific direc- 
tions for making them. 

RECORD OF THE TEST. 

A " log ft of the test should be kept on properly prepared 
blanks, containing headings as follows : — 



Time. 



Piu 


ASSURES. 


r J 


'empbiuturbs 




Fuel, 


Feed W a 






















^j 




b£ 


<v 




g 














a; 


OS 


be 


oS 


o 
o 


a> 















bfj 


oS 




03 
















bfi 


o3 








as 






g 












g 




h3 




o 


p 

o3 


s 




<V 


o 


hie 
eed 


cS 
0) 


S 


* ! 
° 


S 




ft 


cc 


A 


ft 


ft 


ft ft 


CO 


H 


ft 


H 


ft 


















i 







REPORTING THE TRIAL. 

The final results should be recorded upon a properly prepared 
blank, and should include as many of the following items as are 
adapted for the specific object for which the trial is made. The 
items marked with a * may be omitted for ordinary trials, but are 
desirable for comparison with similar data from other sources. 



412 



HANDBOOK ON ENGINEERING. 



Resources of the trials of 

Boiler at 

To determine .... 

1. Date of trial . 

2. Duration of trial . 



DIMENSIONS AND PROPORTIONS. 

3. Grate-surface wide long area 

4. Water-heating surface 

5. Superheating surface 

6. Ratio of water-heating surface to grate- 

surface • . 

AVERAGE PRESSURES. 

7. Steam pressure in boiler, by gauge 

*8. Absolute steam pressure 

*9. Atmospheric pressure, per barometer 
10. Force of draught in inches of water . 

AVE RAGE TEM PE RAT D RES . 

* ] 1 . Of external air 

*15. Of lire-room 

*13. Of steam 

14. Of escaping gases 

15. Of feed-water 



FUEL. 

16. Total amount of coal cousumed . 

17. Moisture in coal 

18. Dry coal consumed 

19. Total refuse, dry pounds equals . 

20. Total combustible (dry weight of coal, 

item 18, less refuse, item 19) . 
*21. Dry coal consumed per hour 
*22. Combustible consumed per hour . 



hours . 
hours. 

Sq. ft. 
Sq. ft. 
Sq. ft. 



lbs. 
lbs. 
in. 
in. 

deg. 
deg. 
deg. 
deg. 
deg. 

lbs. 
per cent. 

lbs. 
per cent. 

lbs.- 
lbs. 
lbs. 



HANDBOOK ON ENGINEERING. 413 

RESULTS OF CALORIMETRIC TESTS. 

23. Quality of steam, dry steam being taken 

as unity 

24. Percentage of moisture in steam . . , percent. 

25. Number of degrees superheated . . . deg. 

WATER. 

26. Total weight of water pumped into boiler 

and apparently evaporated .... lbs. 

27. Water actually evaporated, corrected for 

quality of steam lbs. 

28. Equivalent water evaporated into dry 

steam from and at 212° F. . . . . lbs. 

*29. Equivalent total heat derived from fuel 

in B. T. U B. T. U. 

*30. Equivalent water evaporated in dry 

steam from 212° F. per hour . . . lbs. 

ECONOMIC EVAPORATION. 

31. Water actually evaporated per pound of 

dry coal, from actual pressure and 

temperature . lbs. 

32. Equivalent water evaporated per pound 

of dry coal, from 212° F lbs. 

33. Equivalent water evaporated per pound 

of combustible from and at 212° F. . lbs. 

COMMERCIAL EVAPORATION. 

34. Equivalent water evaporated per pound 

of dry coal with one-sixth refuse, at 70 
lbs. gauge pressure, from temperature of 
100° F., equals item tests 33 X. 0.7249 
pounds lbs. 

f Corrected for inequality of water level and of steam pressure at 
beginning and end of test. 



414 



HANDBOOK ON ENGINEERING. 



RATE OF COMBUSTION. 

35. Dry coal actually burned per sq. foot of 
grate-surface per hour 



*36. 

*37..< 

*38. 



Consumption of 
coal per hour, 
assumed with 
sixth refuse. 



>ur 




lbs 


" 


Per sq. ft. of grate 




dry 
Coal 


surface 
Per sq. ft. of water 


lbs 


one- 


heating surface . 
Per sq. foot of least 


lbs. 


^ 


area for draught. 


lbs 



RATE OF EVAPORATION. 



39. Water evaporated from and at 212° F. per 
square foot of heating surface per hour. 

Per sq. ft. of grate 



*40. 
*41. 

*42. 



Water evaporated per 
hour from temperature 
of 100° F. into steam 
of 70 lbs. gauge pres- 
sure. 



surface . 

Per sq. ft. of heat- 
ing surface 

Per sq. ft. of least . 
area for draught. 



lbs. 
lbs. 
lbs. 



COMMERCIAL HORSE POWER. 

43. On basis of 30 lbs. of water per hour 

evaporated from temperature of 100° F. 
into steam of 70 lbs. gauge pressure 
(341 lbs. from and at 212°) ... H. P. 

44. Horse-power, builders' rating at 

sq. ft. per horse-power 

45. Per cent developed above or below rating per cent. 

* Note. Items 20, 22, 33, 34, 36, 37, 38 are of little practical value. 
For if the result proves to be less satisfactury than expected on the 
actual coal, it is easy for an expert fireman to decrease No. 20 by simply 
taking out some partly consumed coal in cleaning fires, and thus make a 
fine showing on that simply ideal or theoretical unit, the u pound com- 
bustible." The question at issue is always what can be done with an 
actual coal, not the " assumed coal " of items 34, 36, 37 and 38. 



HANDBOOK ON ENGINEERING. 415 

DEFINITIONS AS APPLIED TO BOILERS AND BOILER 
riATERIALS. 

Cohesion is that quality of the particles of a body which causes 
them to adhere to each other, and to resist being torn apart. 

Curvilinear seams* — The curvilinear seams of a boiler are 
those around the circumference. 

Elasticity is that quality which enables a body to return to its 
original form after having been distorted, or stretched by some 
external force. 

Internal radius* — The internal radius is one-half of the diam- 
eter, less the thickness of the iron. To find the internal radius 
of a boiler, take one-half of the external diameter and substract 
the thickness of the iron. 

Limit of elasticity* — The extent to which any material may be 
stretched without receiving a permanent " set." 

Longitudinal seams. — The seams which are parallel to the 
length of a boiler are called the longitudinal seams. 

Strength is the resistance which a body opposes to a disinte- 
gration or separation of its parts. 

Tensil strength is the absolute resistance which a body makes 
to being torn apart by two forces acting in opposite direc- 
tions. 

Crushing strength is the resistance which a body opposes to 
being battered or flattened down by any weight placed upon it. 

Transverse strength is the resistance to bending or flexure, as 
it is called. 

Torsional strength is the resistance which a body offers to 
any external force which attempts to twist it round. 

Detrusive strength is the resistance which a body offers to 
being clipped or shorn into two parts by such instruments as 
shears or scissors. 

Resilience or toughness is another form of the quality of 



416 HANDBOOK ON ENGINEERING . 

strength ;. it indicates that a body will manifest a certain degree 
of flexibility before it can be broken ; hence, that body which 
bends or yields most at the time of fracture is the toughest. 

Working strength. — The term " working strength " implies 
a certain reduction made in the estimate of the strength of ma- 
terials, so that when the instrument or machine is put to use, it 
maybe capable of resisting a greater strain than it is expected on 
the average to sustain. 

Safe working pressure, or safe load. — The safe working pres- 
sure of steam-boilers is generally taken as i of the bursting pres- 
sure, whatever that may be. 

Strain in the direction of the grain, means strain in the direc- 
tion in which the iron has been rolled; and in the process of man- 
ufacturing boiler-plates, the direction in which the fibres of the 
iron are stretched as it j^asses between the rolls. 

Stress. — By the term " stress " is meant the force which acts 
directly upon the particles of any material to separate them. 

HEAT AND STEAM. 

The steam engine is a machine for the conversion of heat into 
])Ower in motion. The heat is' generated by the combustion of 
fuel ; the transmission is accomplished through the agency of 
steam ; the power is made available and brought under control by 
means of the engine. 

The effect of heat upon water is to vaporize it, if there be inten- 
sity enough, the heat will, under proper conditions, cause water to 
boil ; the vapor produced by boiling is called steam, and steam 
under pressure is a product which is the end and aim of that por- 
tion of that steam engine known as the boiler and furnace. The 
steam engine then is to be considered as a form of the heat 
engine ; of which the furnace, boiler, and the engine itself are to 
be regarded as separate portions of the same mechanism. 



HANDBOOK ON ENGINEERING. 417 

The conditions demanded upon economic grounds to secure 
the highest efficiency in the steam engine are : — 

1. A proper construction of the furnace so as to secure the 
perfect combustion of fuel. 

2. The heat generated in the furnace must be transferred to the 
water in the boiler without loss. 

3. The circulation in the boiler must be so complete that the 
heat from the furnace may be quickly and thoroughly diffused 
throughout the whole body of water. 

4. The construction of an engine that will use the steam with- 
out loss of heat, except so much as may be necessary to perform 
work required of the engine. 

5. The recovery of heat from exhaust steam. 

6. The absence of friction and back pressure in the working of 
the engine. 

It is superfluous to say that these conditions are not fulfilled 
in any engine of the present day. At best the combustion of 
fuel is only approximately perfect, the losses being due to several 
causes, among which are, — unburned fuel falling through the 
spaces in the grates and mingling with the ashes. This, with 
some kinds of coal, and improper firing, amounts to a large 
percentage of the furnace waste. It is not possible with any 
present method of setting boilers to transfer all the heat of the 
furnace to the water in the boiler ; nor can there be, for the 
reason that the temperature of the escaping gases must not be 
lower than that of the steam in the boilers, or direct loss will result 
in the radiation of heat from the tubes or flues in the boiler, by 
thus reheating the gases to the steam temperature. If the steam 
pressure is 80 lbs. per square inch above the atmosphere, the cor- 
responding temperature due to this pressure is 324° Fabr. The 
temperature of the escaping gases ought not, therefore, to be less 
than 350° Fahr., where they leave the boiler flues or tubes to pass 
off into the chimney. If the temperature of the furnace be taken 

27 



418 HANDBOOK ON ENGINEERING. 

at 2,000° Fahr,, and the escaping gases at 400° Fahr., it will be 
seen that one-fifth of the heat generated in the furnace is passing 
off without performing work. This is a very great loss, and 
these figures understate, rather than correctly give, the loss from 
this one source. Efforts have been made to utilize the tempera- 
ture of these waste gases by making them heat feed water by 
means of coils, or by that particular disposition of pipes and 
connection known as an economizer. Others have turned it into 
account by making it heat the air supplied the fuel on the grates. 
Any heat so reclaimed is money saved, provided it does not cost 
more to get it than it is worth in coal to generate a similar quan- 
tity of heat. It is doubtful whether the loss in this particular 
direction can be brought below 20 per cent of the fuel burned, at 
least, by any method of saving now known. 

The loss by had firing and by a bad construction of furnace 
is often a large one. It has been demonstrated experimentally 
that 20 to 30 per cent of fuel can be saved by a proper construc- 
tion and operation of the furnace. The direct causes of loss are, 
too low temperature of furnace for properly burning fuels, espe- 
cially such as are rich in hydro-carbon gases ; or, by the admis- 
sion of too much cold air over or back of the fire ; or, by the 
admission of too little air under the fire so that carbonic oxide gas 
is generated instead of carbonic acid gas, the former being a 
product of incomplete, the latter the product of complete 
combustion. The relative heating powers of fuel burned, resulting 
in the production of either of these two gases being as follows : — 

Heat Units. 
1 pound of carbon burned to carbonic acid gas . . 14,500 
1 pound of carbon burned to carbonic oxide . . . 4,500 



Units of heat lost by burning to carbonic oxide . 10,000 
It will be seen that here is an enormous source of loss, and all 
that is required to prevent it is a proper construction of furnace. 



HANDBOOK ON ENGINEERING. 419 

Smoke is a nuisance which ought to be prohibited by stringent 
legislation. There is no good reason for its polluting presence in 
the atmosphere, defiling everything with which it comes in con- 
tact. Smoke regarded as a source of direct loss is greatly over- 
estimated ; the fact is, the actual amount of coal lost to produce 
smoke is very trilling. The presence of smoke indicates a low 
temperature of furnace or combustion chamber ; if the temper- 
ature were sufficiently high and the furnace properly constructed, 
smoke could not be generated. The prevention of smoke is 
easily accomplished, and with it a more economical combustion 
of hydro-carbon fuels. 

Radiation* — A considerable loss of heat occurs by radiation 
from the furnace walls ; this may be prevented in part by making 
the walls hollow, with an air space between. If a force blast is 
used the air may be admitted at the back end of the boiler-setting 
and by passing through between the walls will become heated, 
and if conveyed into the ash pit at a high temperature will greatly 
assist combustion and thus tend to a higher economy. 

Air required* — In regard to the quantity of air required, it 
will vary somewhat with the fuel used, but in general, 12 pounds 
of air are sufficient to completely burn one pound of coal ; prac- 
tically, however, 15 to 25 pounds are furnished, being largely in 
excess of that which the fire can use, and must pass off with the 
gases as a waste product. This surplus air enters cold and 
leaves the furnace heated to the same temperature as that of the 
legitimate and proper products of combustion, and thus directly 
operates to the lowering of the furnace temperature. 

Measurement of heat. — A heat unit is that quantity of heat 
necessary to raise the temperature of one pound of water one 
degree, from 39° to 40° Fahr., this being the temperature of the 
greatest density of water. A thermal unit, a heat unit, or unit 
of heat, all mean the same thing. Experiments have been made 
to determine the mechanical equivalent of a heat unit, and it is 



420 HANDBOOK ON ENGINEERING. 

found to be equal to 772 pounds raised one foot high. This is 
sometimes called "Joule's equivalent," after Dr. Joule, of 
England ; it is also known as the dynamic value of a heat unit. 
Knowing the number of heat units in a pound of coal enables 
us to calculate the amount of work it should perform. Let us 
suppose a pound of coal to be burned to carbonic acid gas, 
and to develop during its combustion 14,000 heat units, then: 
14,000x772 equals 10,808,000 foot pounds. 

That is to say, if one pound of coal were burned under the 
above conditions it would have a capacity for doing work repre- 
sented by the lifting of ten millions of pounds one foot high 
against the action of gravity. Suppose this to be done in one 
hour, then we should expect to get from one pound of coal an 
equivalent of 5.45 H. P. It is well known that only a very 
small fraction of such equivalent is secured in the very best 
modern practice. The question is, where does this heat go, 
and why is it so small a portion of it is actually utilized? The 
losses may be accounted for in several ways, and, perhaps, as 
follows : — 

The heat wasted in the chimney .... 25 per cent. 

Through bad firing . 10 " 

Heat accounted for by the engine (not indicated) 10 " 
Heat by exhaust steam 55 " 

100 per cent. 
This is about 2 pounds of coal per hour per indicated horse 
power, which is regarded as a very high attainment, and is 
seldom reached in ordinary cut-off engines. It requires good 
coal, good firing, and an economical engine to get an indicated 
horse power from two pounds of coal burned per hour. As 
coal varies in quality it is a better plan to deduct the ashes 
and other incombustible matter, and take the net combustible 
as a basis of comparison* The best coal when properly burned 



HANDBOOK ON ENGINEERING. 421 

is capable of evaporating 15 pounds of water from and at a 
temperature of 212° Fahr. The common evaporation is about 
half that amount, and with the best improved furnaces and care- 
ful management, it is seldom that 10 pounds of water is exceeded, 
and is to be regarded as a high rate of evaporation. In experi- 
mental tests, 12 pounds have been reported, but it is doubtful 
whether there is any steam boiler and furnace which is con- 
stantly yielding any such results. 

Circulation of water in a boiler is a very important feature to 
secure the highest evaporative results. Other things being equal, 
the boiler which affords the best circulation of water will be found 
to be the most economical in service. Circulation is greatly hin- 
dered in some boilers by having too many tubes ; in others, by 
introducing in the water space of the boiler too many stays and 
making the water spaces too narrow. To secure the highest 
economy there must be thorough circulation from below upwards, 
in the boiler. There is no doubt that a great deal of heat is lost 
because the construction is such as to hinder a free flow of water 
around the tubes and sides of the boiler. 

The construction of an engine that will use steam without loss 
of heat, except so much as may be necessary to perform work 
required of it', is a physical impossibility. Among the sources of 
loss in an engine are: radiation, condensation of steam in mi- 
jacketed cylinders, and the enormous loss of heat occasioned by 
exhausting the steam into the atmosphere. 

Radiation is usually classed among the minor losses in a steam 
engine. There is a considerable loss of heat caused by radiation 
from steam boilers and pipes exposed to the atmosphere, and not 
protected by a suitable covering. Much of this heat may be 
saved by employing a non-conducting material as a covering, 
which, though not preventing all radiation, will save enough heat 
to make its application economical. It is well known that some 
bodies conduct and radiate heat less rapidly than others, but it 



i22 HANDBOOK ON ENGINEERING. 

must not be understood that the absolute value of such a cover- 
ing is inversely proportioned to the conducting power of the 
material employed, because, in its application, the outer surface 
is enlarged and the radiation will be going on less actively at any 
given point, but the enlarged surface exposed reduces somewhat 
the apparent gain. 

SELECTION OF A BOILER. 

The selection of a boiler for a particular service will naturally 
suggest the following questions : — 

1. What kind of a boiler shall it be? 

2. Of what material shall it be made? 

3. What size shall it be in order to furnish a certain power? 
In reply to the first question, it is to be expected there will be 

wide differences of opinion, varying with the locality, usage, and 
service for which it is intended. One of the first things to be 
taken into account in the selection of a boiler is the quality of 
water to be used in it for generating steam. If the water is pure, 
then it makes little difference what kind of boiler be selected, so 
far as incrustation affects selection. If the water is hard and 
will deposit scale upon evaporation, then a boiler should be 
selected which will admit of thorough inspection and removal of 
any deposit formed within it. 

For hard water, the ordinary flue boiler will be found a good 
' one, as it is favorable to a thorough circulation of water, and 
permits easy access to all parts of it for examination and clean- 
ing. It does not, however, present the extent of heating surface 
for a given space that tubular boilers offer ; but with hard water 
the boiler is quite as economical if kept in good condition. 

The difficulty with tubular boilers when used in connection 
with hard water is that the tubes will in a short time become 
coated with scale ; this prevents the transmission of heat, not 
only, but impairs the circulation of the wafer around them. 



HANDBOOK ON ENGINEERING. 428 

Both of these are opposed to economy in the fact that it requires 
more eoal to generate a given weight of steam in the first case ; 
and second, by reason of deficient circulation the plates over the 
fire are likely to become overheated and burnt and so become 
dangerous ; thus directly contributing to accident or disaster. 

The matter of circulation in boilers is one which should have 
careful attention in making a selection. There is little trouble in 
this regard with any of the ordinary types of 1 (oilers so long as 
they are clean and new, and properly proportioned. Nor is there 
likely to be any difficulty thereafter if the water is soft and clean. 
Circulation is often seriously impaired by putting in too many 
tubes in a boiler, the effect of which is to so fill up the space that 
the heated particles of water forcing their way upwards from 
below meet with so much resistance that they can hardly over- 
come it, and the result is that a boiler does not furnish from one- 
fourth to one-half as much steam for a given weight of fuel as it 
should, from this very cause. 

Boilers intended for use in distant localities where the facilities 
for repairs are meager or entirely wanting, and fuel low priced, 
should be of the simplest description. Cylinder boilers or two- 
tlue boilers will perhaps be found most suitable. These are 
largely used by coal miners, blast furnaces, saw mills, and other 
branches of industry, which must, of necessity, be removed from 
the larger towns and engineering work shops. 

In selecting a boiler for a mill of any kind where they burn 
shavings or offal, or any other place in which the fuel is of 
a similar description and the firing irregular, there should be 
large water capacity in the boiler that it may act as a reser- 
voir of power in much the same way that a fly wheel acts as 
a regulator for a steam engine. It is a common notion among 
wood- workers that firing with shavings or light fuel is " easy 
on the boiler." There is abundant reason to doubt this. 
The suddenness and rapidity with which an intense fire is kin- 



424 HANDBOOK ON ENGINEERING. 

died in the furnace, filling all the furnace space and the tubes with 
flame, and with an intense heat which envelops all within the limits 
of draft opening, continuing thus for a few minutes only, and as 
suddenly going out, can hardly be regarded as the ideal furnace. 
Yet there are thousands of just such furnaces at work, and it is 
altogether probable that little or no change will be made in them 
by this class of manufacturers, at least in the near future. In 
regard to the selection of a boiler for this service, we are brought 
back again to the question of hard or soft water. The decision 
should be largely influenced by this, but whatever type of a boiler 
is selected there should be a surplus of boiler power of at least 20 
per cent, that is, if a 50 horse-power boiler is needed to do the 
Work, put in one of 60 horse-power ; this will prevent the fluctua- 
tions of speed in the engine which are sure to follow a reduction of 
boiler pressure. 

This increase in boiler power ought not to be simply that of 
tube surface, but should also include extra water space. The 
reserve power of a boiler is in the water heated up to a temperature 
corresponding to the steam pressure ; when this pressure is 
lowered, the water then gives off steam corresponding to the lower 
pressure ; the more water the more steam ; and in this way the 
water in the boiler stores up heat when overfired, to give it off 
again when the fire is low, and so acts a regulator of pressure, a 
thing that extra tube surface cannot do. This kind of firing is 
apt to induce priming, and for this reason a boiler should be 
selected having a large water surface. Horizontal boilers are, in 
general, to be preferred over vertical ones for mills, because of the 
larger water surface exposed in proportion to the heating surface. 
If a tubular boiler is selected, the water line above the tubes 
should be not higher than two-thirds the diameter of the boiler 
measured from the bottom, and the bo'iler should be made having 
the upper edge of the top row of tubes at least three inches below 
this ; there should also be a clear space up through the center of 



BANDBOOK ON ENGINEERING, 425 

the boiler of sufficient width to insure a perfect circulation of 
water. 

Horizontal tubular boilers are to be recommended when pure 
soft water is used. They combine at once the qualities of great 
strength without excessive bracing, large heating surface., high 
evaporative capacity without liability to priming, and are conve- 
nient of access for external and internal examination when set in 
the furnace. 

Fire box boilers, or locomotive boilers, as they are commonly 
called, are best adapted for small powers and with a fuel which 
deposits but little soot in the tubes. This kind of boiler is sup- 
plied with portable or agricultural engines and is very well adapted 
for that particular service. In canvassing the desirability of 
this kind of a boiler for stationary use, we must again refer to the 
kind of water to be used in it. If the water is soft and clean 
there is then no particular objection to a boiler of this construc- 
tion being used for small powers ; if the water is hard and will 
form scale, it ought not to be chosen, but a flue boiler selected 
instead. 

Vertical boilers are used in great numbers for small engines, 
heating, etc. They have the merit of being compact and low 
priced. A common defect in the construction of this kind of 
boiler is that too many tubes are put in the head in the fire box, 
thereby preventing a proper circulation of water between them. 
This defect in construction induces priming, with all its attendant 
annoyances and dangers. This style of boiler is not suited to 
hard water, but pure soft water only. These boilers should be 
provided with hand holes above the crown sheet and around the 
bottom of the water legs ; at least three at each place mentioned . 
In regard to the material of which a boiler shall be made there is 
but the simple choice between iron and steel. 

Steel for boilers should not be of too high tensile strength ; 
55,000 to 60,000 pounds tensile strength per square inch makes 



42(i HANDBOOK ON ENGINEERING. 

the best boilers. If the steel is of too high a grade it will take a 
temper, and, therefore, is utterly unlit for use in steam boilers ; 
if the steel is of too low tensile strength it is apt to be loose or 
spongy. Among the advantages steel possesses over iron may be 
mentioned the circumstanee that it is a practically homogeneous 
material when properly made and rolled, consequently, it is nearly 
as strong in one direction as it is in another. In this respect, 
steel is superior to iron plate of equal thickness, because the latter 
is made up of several pieces of iron welded together and in rolling 
into the plate it becomes fibrous, and thus of unequal strength, 
being greatest in the direction of the fiber, and least, when tested 
across it. 

BOILER TRIMMINGS. 

The common trimmings to a steam boiler are a safety valve, 
feed and blow-off pipe, steam pipe, gauge cocks, glass water gauge 
and steam gauge ; to which may be added a steam drum or dome 
and a mud drum. There are numerous other devices which are 
attached to boilers such as safety gauges, alarms, fusible plugs, 
automatic dampers, etc. ; many of these are very serviceable and 
are well liked by those using them. 

Safety valves should always be large enough to permit the 
escape of all the steam a boiler is capable of making and each 
boiler should have its own safety valve rather than connecting two 
or more boilers together and depending on one valve for the 
whole. The valve and seat should be made of hard gun metal, or 
any other composition that will not rust and stick fast. At one 
time it was quite a common thing to see a brass valve fitted to a 
cast-iron seat ; this is wrong, for the rusting of the iron would Hk 
the valve so tightly that the boiler would be in constant danger of 
rupture from over pressure. For stationary boilers the common 
ball and lever safety valves are generally used. For stationary 
boilers it is immaterial whether the safety valve be fitted with a 



HANDBOOK ON ENGINEERING. 427 

lever and weight, or whether it be fitted with a spring. The 
former is the usual manner of loading a safety valve and has hut 
few objections. For portable engines and locomotives safety 
valves are loaded with springs, which by suitable adjustment may 
be made to blow off at any desired pressure. 

The following' rule is that enforced by the U. S. Government 
in fixing the area of safety valves for ocean and river service, when 
the ordinary lever and weight safety valve is employed : — 

Rule* — When the common safety valve is employed it shall 
have an area of not less than one square inch for each two square 
feet of grate surface. 

Another rule is to multiply the pounds of coal burned per 
hour by 4 ; this product is to be divided by the steam pressure, 
to which a constant number 10 is added. 

Example : What would be the proper area for a safety valve 
for a boiler having a grate surface 5 feet square and burning 12 
pounds of coal per hour per square foot of grate ; the steam 
pressure being 75 pounds per square inch? 

5x5 equal 25 square feet of grate. 

25 x 12 equal o00 lbs. Of coal per hour. 

300x4 equal 1200. 

75 plus 10 equal 85 equal steam pressure with 10 added, then 
1200/85 equal 14.11 inches area, or 4| inches diameter. 

A feed pipe should be at least twice the area over that wdrich is 
regarded as simply necessary to supply the boiler with water, as 
sediment or scale is likely to form in it, which will materially re- 
duce its ' area. In localities where the water is hard the feed 
pipes should be disconnected near the boiler and examined occa- 
sionally to ascertain whether or not scale is forming in them. 

In general* the sizes of feed pipes leading from the pump 
to the boiler are fixed by the size of tap used by the maker of 
the pump. It is not well to reduce the diameter of the pipe and 
the size should be the same throughout. Care should be exer- 



4*28 HANDBOOK ON ENGINEERING. 

cised, in putting pipes in place that no strain be brought upon them 
by imperfect fitting, as it is certain to lead to leaky joints at some 
time or other. It is also desirable that the pipes be as short and 
straight as possible. Feed pipes should never be place/1 under 
ground if it is possible to make any different disposition of them. 
In locating pipes it is desirable to arrange for the expansion of 
the boiler, as well as for that of the pipes themselves. In select- 
ing a pump it should have a much larger capacity than that needed 
to supply the boiler, as there are many things which affect the 
working of a pump, such as a defective suction pipe, leaky valves, 
etc. It is the practice of most manufacturers to give the capacity 
of their pumps in gallons of water delivered per minute, from 
which it is easy to select a suitable size ; but the speed given in 
the tables at which the pump is to run is generally faster than 
that which it is desirable to run them. As a general thing, and 
without referring to any particular maker or design, it is a good 
plan to select a pump having four times the capacity actually 
needed for the boiler ; then the speed may be reduced to half that 
given in the table, and will require less repairs, and will be a more 
satisfactory purchase in the long run. 

In selecting an injector or inspirator, the size should not 
greatly exceed that actually required to supply the boiler. In 
making the steam connections the pipes should start from the 
steam space of the boiler and should not be branches merely from 
the other steam pipes ; neither should the diameters of the pipes 
be less than that which the instrument calls for. The pipes 
should be as short and straight as practicable ; abrupt bends 
should always be avoided in the suction pipes. If the water is 
taken from a place in which there are floating particles of wood, 
leaves, etc., a strainer should be used ; a large sheet metal box 
with perforated sides, makes a good strainer ; the openings ought 
not too greatly exceed an eighth of an inch in diameter, and should 
be several times the area of the suction pipe. 



Handbook on engineering. 4^9 

A check valve should be fitted with a valve between it and the 
boiler, so that in the event of its not working satisfactorily it may 
be taken apart, cleaned and replaced without stopping for exami- 
nation or repairs. 

The blow-off pipe should be so arranged that it will entirely 
drain the boiler of water ; it is also a good plan to set a boiler 
with a slight inclination toward the blow-off pipe that it may be 
thoroughly drained; an inclination of two inches in twenty feet 
works well in practice. The blow-off pipe is usually fitted at the 
back end of the boiler. 

The steam pipe may be connected at any convenient point on 
the top of the boiler. If the boiler is to furnish steam for an 
engine only, the common practice is to make the diameter of the 
pipe one-fourth that of the cylinder. The steam pipe should be 
as short and straight as possible. If bends are to be introduced 
in steam pipes it is better to have a long curved bend than the 
abrupt right-angle fitting usually employed for the purpose. It 
is also a good plan to provide a stop-valve r xt to the boiler to 
shut off the steam and prevent it condensi^^ in the steam pipe at 
night, or other long stoppages. 

The gauge cocks should not be less than three in number, and 
ma} r be of any of the various kinds now in the market. For 
stationary boilers, the Mississippi gauge cock is, perhaps, as 
good as any. For portable engines a compression gauge-cock is, 
perhaps, the best. The lower gauge-cock should be at least 
2" above the tubes or crown sheet, the middle 2" above the first 
ordinary water line, the upper 2" above the 2 on 2" to 3", de- 
pending on the size of the boiler. 

A glass water gauge should be provided for each boiler and 
should be so located that the water level in the boiler when at the 
lower end of glass shall be one inch above the top of flue. When 
glass gauges are so fitted the fireman can always tell at a glance 
just how much water he has above the flues or crown sheet ; it 



430 HANDBOOK ON ENGINEERING. 

also permits the easy test of accuracy by trying the gauge-cocks 
with the water at a certain known level. Too much dependence 
must not be placed on the glass water-gauge alone, but should be 
used in connection with the gauge-cocks. 

A steam gauge is a very important appendage to a steam 
boiler, and should be chosen with special reference to accuracy 
and durability. The ordinary gauges now in the market are the 
bent tube and the diaphragm gauges. It matters little which of 
the two kinds is selected, provided it is a good and first-class 
gauge. A steam gauge should be compared with a standard test 
gauge at least once a year, to see that it is correct. The 
importance of this will be fully apparent when it is known that it 
furnishes the only means by which the fireman is to judge of the 
steam pressure in the boiler. A siphon should be attached to 
every gauge, and provision should also be made for draining the 
gauge or siphon, to prevent freezing when steam is off the boiler. 
Neglect of this may endanger the accurate reading of the steam 
gauge and render it useless. 

Steam dome. — This is a reservoir for steam riveted to the 
upper portion of the shell and communicated by a central opening 
with the steam space in the boiler. When this reservoir forms a 
separate fixture and is attached to the boiler by cast or wrought 
iron nozzles, it is then called a steam dram. The latter answers 
all the purposes for stationary boilers that the former does, and 
is to be preferred because of the smaller openings in the shell of 
the boiler. A considerable number of boiler explosions have 
been traced directly to the weakness of the shell, caused by the 
large opening in and imperfect staying of the shell underneath 
the dome. When a dome is employed and has a large hole under- 
neath, the strength of the shell is impaired in two ways: 1. By 
reducing the longitudinal sectional area of shell through the cen- 
ter of opening cut for it, which weakness cannot wholly be made 
good by a strengthening ring around the opening. 2. By causing 



HANDBOOK ON ENGINEERING. 431 

a tension equal to that on the crown area of steam dome, upon 
the annular part of the shell covered by the flange of the dome. 
The weakest part of the boiler shell will be where the distance 
from rivet hole at the base of the dome to edge of plate is least. 
It is difficult, owing to the complex nature of the strains, to form 
a rule whereby to determine how much the strength of the shell 
is impaired by using a dome ; but it is quite apparent from gen- 
eral experience that they are in many cases a source of weakness, 
and the larger the dome connection with the shell, the greater the 
liability to rupture. This tendency to rupture is due to the fact 
that the dome, with its connecting flange, is practically inelastic ; 
that portion of the shell of the boiler covered by the dome is, as 
soon as the pressure is introduced on both sides of the plate, 
simply a curved brace. The pressure of the steam in the boiler 
has a tendency to straighten the shell under the dome and thus 
brings about a series of complex strains which are not easily rem- 
edied by any system of bracing, so that on the whole it is prefer- 
able to use a small connecting nozzle with a drum above it, rather 
than to rivet a large dome directly to the shell. 

Dry pipe* — This is a pipe having numerous small perforations 
on its upper side, and inserted in the upper part of the steam space 
of the boiler. This pipe does not dry the steam, but acts 
mechanically by separating the steam from the water when the 
latter is in a violent state of agitation, and is liable to be carried 
in bulk toward or into the steam pipe. The object of these numer- 
ous small holes in the pipe is that a small quantity of steam may 
be taken from a large number of openings at one time, and thus 
carried over a larger extent of surface than that afforded by a 
single opening, and by this single device checking the tendency to 
priming. 

Steam boiler furnaces are receiving more attention now than 
perhaps ever before. The question of economy of fuel is being 
closelv studied, and there is now an effprt to save much of the 



432 HANDBOOK ON ENGINEERING. 

heat which had formerly been allowed to go to waste. The main 
thing in furnace construction is to get perfect combustion. With- 
out this there must be of necessity a great loss constantly going 
on. There are some losses which it is difficult to prevent, for 
example — the loss by the admission of too much air in the ash 
pit ; the loss by incomplete combustion ; the loss occasioned by 
the heated gases escaping up the chimney ; the loss by radia- 
tion ; but, chief among these, is that of incomplete combustion. 
To burn a pound of coal requires about twenty -four pounds of air, 
or, say 300 cubic feet. Most boiler settings permit from 200 to 300 
feet to pass through the fire. It is needless to point out the 
great source of loss arising from this one cause alone. This may 
be prevented in a measure by having a suitable damper in the 
chimney, and regulating the flow of escaping gases by it, instead 
of the ash pit doors. If the furnace is so constructed that the 
fuel is imperfectly burned, so that carbonic oxide instead of car- 
bonic acid gas is formed, the loss is very great. This results 
often from too little air supply and too low temperature in the 
furnace. The furnace doors should be provided with an opening 
leading into the space between the door proper and the liner ; 
this opening ought to have a sliding or revolving register by which 
the admission of air may be controlled. By this means, the 
quantity of air admitted above the fire may be adjusted^ to its 
needs by a little attention on the part of the fireman. The liner 
to the furnace door should have a number of small holes in it, 
rather than a solid plate, with a space around the edges. Great 
care should be exercised in the construction of furnace walls, 
that the materials and workmanship be good throughout. The 
entire structure should be brick. The outer walls may be of. 
good hard red brick, but the interior walls, around the furnace 
and bridge wall, should be of fire brick. The best quality of fire 
brick for withstanding an intense heat are very, very strong and 
tenacious ; the structure is open and they are free from black 



HANDBOOK ON ENGINEERING. 433 

spots, due to sulphuret of iron in the clay ; if well burned they 
will not be very light colored on the outside, and will have a 
clear ring when struck. 

Fire brick should be dipped in a thin mortar made of lire clay, 
rather than in a lime and sand mortar, such as is used in ordinary 
red brickwork. In laying up these portions of a boiler furnace 
requiring lire brick, provision should be made in the original wall 
for replacing the fire brick and without disturbing the outer 
brickwork. 

CARE AND MANAGEMENT OF A BOILER. 

It is not enough that a boiler be of approved design, made of 
the best materials, and put together in the best manner ; that it 
have the best furnace and the most approved feed and safety 
apparatus. These are all desirable, and are to be commended, 
but cleanliness and careful management are quite essential to get- 
ting high results, and are also conducive to long use in service. 

Pumps* — Special attention should be given at all times to the 
feed and safety apparatus ; the pumps should be in good working 
order ; it is preferable that they be independent steam pumps 
rather than pumps driven by the engine, or by a belt ; they should 
be kept well packed and the valves in good condition . 

Firing* — Kindle a lire and raise steam slowly ; never force a 
*fire so long as the water in the boiler is below the boiling point. 
The fire should be of an even height, and of -such a thickness as 
will be found best for the particular fuel to be burned, but should 
be no thicker than actually necessary. In regard to the size of 
coal used, that will depend upon circumstances. If anthracite 
coal is used, it should- not, for stationary boilers, be larger than 
ordinary stove coal. For bituminous coal, which is always shipped 
in lumps as large as can be conveniently handled, the size will 
vary somewhat in breaking, but it may in general be used in 
larger lumps than anthracite. If the coal is likely to cake in burn- 

W 



4o4 HANDBOOK ON ENGINEERING. 

ing, the fire should be broken up quite frequently with asliee bar, 
or it will fuse into a large mass in the center of the furnace and 
lower the rate of combustion. If the coal is likely to form a con- 
siderable quantity of clinker, or enough to become troublesome, it 
may be- advantageous to increase the grate area and thus lower 
the rate of combustion per square foot of grate, and have a fire of 
less intensity. The fire should be kept free from ashes, and the 
ash pit should be kept clean. Whenever the fire door of a steam 
boiler furnace is opened, the damper should be closed to prevent 
the sudden reduction of temperature underneath, which is likely 
to injure the boiler by contraction, and thus render it likely to 
spring a leak around the riveted joints. Some firemen are very 
careless in this respect, and there is little doubt that many a dis- 
agreeable job of repairing a leaky seam might be prevented by 
this simple precaution. 

Gauge cocks should be used constantly to keep them free from 
any accumulation of sediment. It is a very common practice to 
rely wholly on the indications of the glass water gauge for the 
water level in the boiler. This is all wrong and should be dis- 
continued, if once begun. The glass water gauge serves a very 
useful purpose, but it should not be wholly relied on in practice. - 
In using the ordinary gauge cocks, the ear more than the eye, 
detects the water level, and thus acts as a check on the indications 
given by the glass gauge. 

Water gauges should be tested several times during the day to 
see that they are clear, and to keep them free from any sediment 
likely to form around the lower opening to the water in the 
boiler. If this is not attended to, the water gauge is likely to 
indicate a wrong water level and a serious accident may be the 
result. 

Steam or pressure gauges are likely to become set after long 
use and should be tested at least once, or better still, twice a year 
by a standard gauge known to be correct. They should also be 



HANDBOOK ON ENGINEERING. 435 

tested every few days if the boilers are constantly under steam 
by turning off the steam and allowing the pointer to run back to 
zero. If there are two or more boilers set together in one battery, 
and each boiler has its own steam gauge, and which will, starting 
from the zero point, indicate the same pressure on all the gauges, 
they may be assumed to be correct. 

Blow-off cocks or valves should be examined frequently and 
should never be allowed to leak. In general a cock is to be pre- 
ferred to a valve, but both is safer than one ; if the latter is 
selected it should be some one of the various ' ; straight-way 
valves," _ of which there are now several in the market. If the 
cock is a large one, and especially if it has either a cast iron shell 
or plug, it should be taken apart after each cleaning out of the 
boilers, examined, greased with tallow and returned. 

Blowing- out. — This should be done at least once a day, 
except in the very rare instances in which water is used that will 
not form a scale. The water should not be let out of a boiler or 
boilers until the furnace is quite cold, as the heat retained in the 
walls is likely to injure an empty boiler directly by overheating* 
the plates, and indirectly by hardening the scale within the 
•boiler. Bad effects are likely to follow when a boiler is emptied 
of its water before the side walls have become cool ; but greater 
injury is likely to result when cold water is pumped into an empty 
boiler heated in this manner. The unequal contraction of the 
boiler is likely to produce leaky seams in the shell and to loosen 
the tubes and stays. It is a better plan to allow the boiler to 
remain empty until it is quite cold, or sufficiently reduced in tem- 
perature to permit its being filled without injury. Many boilers, 
of good material and workmanship have been ruined by the 
neglect of this simple precaution. 

Fusible plug's should be carefully examined every six months, 
as scale is likely to form over the portion projecting into the 
water space. It is only a question of time when this scale 



43(5 HANDBOOK ON ENGINEERING . 

would form over the end of the plug, and thick enough to with- 
stand the pressure of steam and thus fail in the accomplishment of 
the very object for which it was introduced. This applies espe- 
cially to the fusible plugs inserted in the crown sheets of portable 
engine boilers. 

Cleaning tubes* — This should be done every day if bitumin- 
ous coal is used. A portable steam jet will be found an extremely 
useful contrivance which will keep them reasonably clean by blow- 
ing out the loose soot and ashes deposited in the tubes. Every 
two or three days, or at least once a week, a tube scraper or stiff 
brush should be used to take out all the ashes or soot adhering 
to the tubes and which cannot be blown out with the jet. Flues 
may be cleaned the same way but will not require to be done so 
frequently. 

Low water* — If from any cause the water gets low in the 
boiler, bank the fire with ashes or with fresh coal as quickly as 
possible, shut the damper and ash pit doors and leave the fire 
doors wide open ; do not disturb the running of the engine but 
allow it to use all the steam the boiler is making ; do not 
under any circumstances attempt to force water in the boiler. 
After the steam is all used and the boiler cooled sufficiently to be 
safe, then the water may be admitted and brought up to the reg- 
ular working height ; the damper opened and the tires allowed to 
burn and steam, raised as usual; provided, no injury has been 
done the boiler by overheating. 

Foaming" and priming are always troublesome and often danger- 
ous. Some boilers prime almost constantly, because of their bad 
proportion, and will require the constant care of the person in 
charge, especially at such times as the engine may be using the 
steam up to the full capacity of the boiler. In a case of this kind, 
an increase in pressure will often check, but will not entirely 
prevent it ; nothing short of an increase of water surface, or a 
better circulation of water, or a larger steam room will afford a 



HANDBOOK ON ENGINEERING. 437 

complete remedy. If the foaming or priming is clue to a sudden 
liberation of steam, or on account of impure feed water it may be 
checked by closing the throttle valve to the engine and opening 
he fire door for a few minutes. The surface blow may be used 
with advantage at this time, by blowing off the impurities collected 
on the surface of the water. The feed pump may be used if 
necessary, but care should be exercised that too much cold water 
be not forced into the boiler, and thus lose time by having to 
wait for the accumulation of the regular steam pressure required 
for the engine. The dangers attending foaming or priming are :. 
the laying bare of heating surfaces in the boiler, and of breaking 
down the engine by working water into the cylinder. The com- 
monest damage to the engine being either the breaking of a cylin- 
der head, or the cross-head, or the breaking of the piston. Wben 
boilers are new and set to work for the first time priming is a very 
frequent occurrence ; in fact, it may be said that for the first few 
days there is always more or less of it. All that is needed during 
this time is a little care on the part of the attendant to see that 
the water is kept up to the required level in the boiler ; it is also 
rceommended that the throttle valve to the engine be partially 
closed to prevent any very great variation of pressure in the 
boiler, and thus prevent water passing over with the steam 
in such quantities as to become dangerous. If a boiler 
continues to prime after it has had a week's work and 
then thoroughly cleaned, the causes are to be attributed to 
other than the grease and dirt in it, which are inseparable from 
the manufacture. As already said, priming may be caused by a 
sudden reduction of pressure ; that is, a boiler may be working 
smoothly and well with say 80 pounds pressure ; if an increase 
of load be suddenly applied to an engine so as to reduce the 
pressure to 70 or 60 pounds, this sudden reduction of pressure 
will almost always cause priming ; the less the steam space in the 
boiler, the greater the tendency to prime, and the greater the 



438 HANDBOOK ON ENGINEERING. 

difficulty in checking it'. The only permanent cure for this is 
more boiler power ; as a temporary expedient, the engine should 
be throttled sufficiently to make the drain upon the boiler con- 
stant instead of intermittent. If the duty required of an engine 
is irregular, the steam pressure should be carried higher ; in any 
case similar to the above, it is recommended that the pressure be 
increased to 90 or 100 pounds and the throttling to begin with 
the increased drain upon the boiler. But this is at best a mere 
makeshift, and a larger 1 toiler power becomes imperative both 
on the score of economy and safety. 

WATER FOR USE IN BOILERS. 

Water is never pure, except when made so in a laboratory or 
by distillation ; the impurities may be divided into four classes : 
1. Mechanical impurities. 2. Gaseous impurities. 3. Dissolved 
mineral impurities. 4. Organic impurities. 

(a) Mechanical impurities may be both mineral and organic. 
The commonest suspended impurity in water is mud or sand; 
these may be removed by nitration or by allowing the water to 
stand long enough to let them settle to the bottom of the tank or 
cistern and then carefully drawing the water from the top, and 
without disturbing the bottom. 

(b) Gaseous impurities in water vary somewhat according to the 
localities from which they are obtained. The commonest gases 
found in the water are an excess of oxygen, nitrogen and carbonic 
acid. These have no effect on water intended for steam boilers. 

(c) Dissolved mineral impurities in water are of the most 
varied description, and are almost always found in it. Among 
these are found salts of iron, sulphate and carbonates of lime; 
sulphate and carbonates of magnesia; salt and alkalies, such as 
soda, potash, etc. ; acids, such as sulphuric, phosphoric, and 
others. All of these are more or less injurious to steam boilers. 
The most objectionable are the salts of lime and magnesia, which 
impart to water that property known as hardness. When such 



HANDBOOK ON ENGINEERING. 4?9 

water is used in a steam boiler a* scale will gradually form, which 
will, in a short time, become very troublesome. 

(d) Organic impurities are present, to a certaiu extent, in 
most waters. They are sometimes present in the water in suffi- 
cient quantities to give it a very decided color and taste. 

The presence of organic matter in water is often dangerous to 
health, and may be a means of spreading contagious diseases, 
but has little or no bad effect in any water used for steam boilers. 
In general, water is regarded by engineers as being either soft, 
hard or salt. 

Ebullition* — Is the motion produced in a liquid by its rapid 
conversion into vapor. When heat is applied to the bottom of a 
boiler, the particles of water in contact with the plates become 
heated and immediately expand, and becoming specifically lighter, 
pass upwards through the colder body of water above ; the heat of 
the furnace is in this way diffused throughout the whole body of 
water in the boiler by a translation of the particles of water from 
below upwards, and from top to bottom in regular succession. 
After a time this liquid mass becomes heated to a degree in which 
there is a violent agitation of the whole body of water, steam is 
given off and it is said to boil. The temperature at the boiling 
point of water, at ordinary atmospheric pressure, is 212° Fahr., 
and increases as the pressure of steam above it increases. 

Distilled water for boilers is not to be recommended without 
some reservation. Chemically pure water, and especially water 
which has been redistilled several times, has a corrosive action on 
iron which is often very troublesome. The effect on steel plates 
by the use of water several times redistilled, such, for example, as 
that supplied for heating buildings, is well known ; information is 
yet wanting which shall point with certainty to the exact change 
which the water undergoes and explain why its action on or 
affinity for steel is so greatly intensified. It has been suggested 
as a means of neutralizing this corrosive action of the water, to 



440 HANDBOOK ON ENGINEERING. 

introduce with the feed other water, which shall have the prop- 
erty of forming a scale and continuing it long enough and at such 
intervals as will permit the formation of a thin scale in the interior 
of the boiler. However objectionable this may seem at first 
sight, it is at present the best practical solution of the difficulty. 
Scale is a bad conductor of heat and is opposed to economical 
evaporation. It is estimated that a thickness of half an inch of 
hard scale firmly attached to a boiler plate will require a temper- 
ature of about 700° Fahr. in the boiler plate in order to raise and 
maintain an ordinary steam pressure of 75 pounds. The mis- 
chievous effects of accumulated scale in the boiler, especially in 
the plates immediately over the fire, are : (1) preventing the water 
from coining in contact with the plates, and thus directly con- 
tributing to the overheating of the latter; and (2) by causing a 
change of structure in the plates and the consequent weakening- 
brought about by this continual overheating, which would, in a 
short time, render an iron or a steel plate wholly unfit for use in 
a steam boiler. The two principal ingredients in boiler scale are 
lime and magnesia. The lime, when in combination with 
carbonic acid, forms carbonate of lime ; when in combination with 
sulphuric acid, it then becomes sulphate of lime. This is also 
true of magnesia. 

Carbonate of lime will form in the boiler as a loose powder 
which is held mechanically in suspenion ; while in this stage it 
may be blown out of the boiler without injury to it ; but it is 
seldom that a pure carbonate is formed in the boiler as there are 
other impurities in the water with which it combines to form a 
hard scale. This is especially true in such waters as also contain 
sulphate of lime in solution. This fine powder (carbonate of 
lime), will form a hard scale should any adhere to the sides or 
bottom of a boiler ; in any case where the boiler is blown out dry 
while the furnace walls are still hot; and this, in itself, forms an 
excellent reason why boilers should stand until the furnace walls 



HANDBOOK ON ENGINEERING. 441 

are cold before blowing out. When emptied, nearly or all of this 
slushy deposit may be washed out of the boiler by means of a 
hose. 

Sulphate of lime is not so easily got rid of, as it is^heavier than 
carbonate of lime and adheres to the plates while the boiler is at 
work. It is the most troublesome scale steam engineers have to 
deal with ; it is very difficult to remove and by successive layers 
becomes dangerous, on account of the thickness to which it 
eventually accumulates. 

The carbonates of lime and magnesia may be largely arrested 
by passing the feed water through a suitable heater and lime 
extractor. It must be apparent to every one that any device 
which will accomplish this is a very desirable attachment to a 
steam boiler. As it is not possible to eliminate all the foreign 
matter in the water from it, recourse is often had to the use of 
solvents and chemical agencies for the prevention of scale. Some 
of these are very simple and within easy reach ; others are sur- 
rounded by an atmosphere of uncertainty and the real nature of 
the compound is hidden under a meaningless trade-mark. For 
carbonate of lime, potatoes have been found to be very service- 
able in preventing the formation of scale ; its action appears to 
be that of surrounding the particles of lime with a coating of 
starch and gelatine, and thus preventing the cohesion of these 
particles to form a mass. Various astringents have been used for 
this purpose, such as extracts of oak and hemlock bark, nutgalls, 
catechu, etc., with varying success. 

Carbonate of soda has been used and with very great success in 
some localities, not only in preventing, but in actually removing 
scale already formed. It acts on carbonate of lime not only, but 
on the sulphate also. It is clean, free from grit, and is quite 
unobjectionable in the boiler ; one or more pounds per day, de- 
pending on the size of the boiler, may be admitted through the 
pump with the feed water ; or admitted in the morning before 



442 HANDBOOK ON ENGINEERING. 

firing up, by simply mixing with water and pouring into the boiler 
through the safety valve or other opening. 

Tannate of soda has been similarly employed and is an excel- 
lent scale preventive. It will also act as a solvent for scale 
already formed in the boiler, acting on sulphate as well as carbon- 
ate of lime. 

Crude petroleum has been found very beneficial in removing 
the hard scale composed principally of sulphate of lime. 

Zinc in steam boilers. — The employment of zinc in steam 
boilers, like that of soda, has been adopted for two distinct 
objects: (1) to prevent corrosion, and (2) to prevent and 
remove incrustation. To attain the first object, it has been used 
chiefly in marine boilers, and for the second, chiefly in boilers fed 
with fresh water. In order that the application of zinc in marine 
boilers may be effective, it is necessary that the metallic contact 
should be insured. If galvanic action alone is relied upon for the 
protection of the plates and tubes, it will doubtless be diminished 
materially by the coating of oxide that exists between all joints of 
plates, whether lapped or butted, and also between the rivets and 
the plates. Assuming the preservative action of zinc to be proved 
when properly applied, we have now two systems for preventing 
the internal decay of marine boilers, viz. : allowing the plates and 
tubes to become coated with scale, and employing zinc. It 
remains to decide which of these two systems is the best with 
respect to economy and practicability. 

We come now to consider the use of zinc for preventing and 
removing incrustation. 

At one time it was considered that the action of zinc in pre- 
venting incrustation was physical or mechanical. The particles 
of zinc, as it wasted away, were supposed to become mixed 
amongst the solid matter precipitated from the water, in such a 
manner as to prevent it adhering together, so as to form a hard 
scale; or the particles of zinc were supposed to become deposited 



HANDBOOK ON ENGINEERING . 443 

upon the plates, and so prevent the scale from adhering to them 
Then it was suggested that the zinc acted chemically, and now, it 
is the generally received opinion that its action is galvanic'in 
preventing incrustation as well as in preventing corrosion. When 
the water contains an excess of sulphates or chlorides over the 
carbonates, the acid of the former will form soluble salts with the 
oxide of zinc, the surface of the zinc will be kept clean, and the 
galvanic current, to which the efficiency of the zinc is due, will be 
maintained. On the other hand, should there be a preponderat- 
ing amount of carbonates, the zinc will be covered first with oxide, 
then with carbonates and its useful action arrested and stopped.' 
It is quite as important that the zinc should be in metallic con- 
tact with the plates when used to prevent incrustation, as when 
employed to prevent corrosion. The application of zinc for the 
former purpose should never be attempted without first having the 
water analyzed in order to ascertain whether it is likely to be 
effective. The use of zinc in externally fired boilers should be 
attempted with great caution, as when efficacious in preventing 
the formation of a hard scale, it is liable to produce a heavy 
sludge that may settle over the furnace plates and lead to over- 
heating. On the whole we cannot but regard the evidence as to 
the effect of zinc upon incrustation as being very conflicting. 

Leaks should be stopped as soon as possible after their dis- 
covery ; the kind of leak will indicate the treatment necessary. 
If it occurs around the ends of the tubes, it may be stopped by 
expanding the tubes anew ; if in a riveted joint, it should be care- 
fully examined, especially along the line of the rivets and care 
should be exercised in determining whether there is a crack 
extending from rivet to rivet along the line of the holes ; should 
this prove to be the case, the boiler is then in an extremely 
dangerous condition and under no circumstances should it be 
again fired up until suitable repairs have been made which will 
insure its safety. 



444 HANDBOOK ON ENGINEERING. 

Blisters occur in plates which are made up of several thick- 
nesses of iron and which from some cause were not thoroughly 
welded before the final rolling into plates. When such a plate 
comes in contact with the heat of the furnace the thinnest portion 
of the defective plate "buckles" and forms what is called a 
blister. As soon as discovered, there should be thorough exami- 
nation of the plate and if repairs are needed there should be as 
little delay as possible in making them. If the blister be very 
thin and altogether on the surface it may be chipped and dressed 
around the edges ; if the thickness is equal or exceeds p" the 
blister should be cut off and patched, or a new plate put in. 

Patching boilers- — When a boiler requires patching it is bet- 
ter to cut out the defective sheets and rivet in a new one ; or if 
this cannot be clone, a new piece large enough to cover the defect 
in the old sheet- may be riveted over the hole from which the 
defective portion has been cut. If this occurs in any portion of 
the boilei subject to the action of fire, the lap should be the same 
as the edges of the boiler seams, and should be carefully calked 
around the edges after the riveting. Whenever the blisters occur 
in a plate, patching is a comparatively simple thing as against the 
repairs of a plate worn by corrosion. In the latter case, the 
defective portions of the plate should be entirely removed and the 
openings should show sound metal all around and of full thick- 
ness. If this cannot be obtained within a reasonable sized open- 
ing then the whole plate should be removed. 

It often occurs that a minor defect is found in a plate and at a 
time when it is not convenient to stop for repairs ; in such an 
event a " soft patch"" is often applied. This consists of a piece 
of wrought iron carefully fitted to that portion of the boiler plate 
needing repairs ; holes are fitted in both plates and patch, and 
« patch bolts " provided for them. A thick putty consisting of 
white and red lead with iron borings or filings in them placed 
evenly over the inner surface of the patch, which is then tightly 



HANDBOOK ON ENGINEERING. 445 

bolted to the boiler plate. This is best but a temporary make- 
shift and ought never to be regarded as a permanent repair. A 
mistake is often made of making a patch of thicker metal than 
that of the shell of the boiler needing it. A moment's reflection 
ought to show the absurdity of putting on a T 5 g or | patch on an 
old i inch boiler shell ; yet it is not so rare as one would imagine. 
A piece of new iron T 3 g" thick will, in most cases, be found to be 
stronger than that portion of a J" old plate needing repairs. 

Inspection* — A careful external and internal examination of a 
boiler is to be commended for many reasons. This should be as 
frequent as possible and thoroughly done ; it should include the 
boiler not only, but all the attachments which affect its working 
or pressure. Particular attention should be paid to the examina- 
tion of all braces and stays, safety valve, pressure gauges, water 
gauges, feed and blow-off apparatus, etc. ; these latter refer more 
particularly to constructive details necessary to proper manage- 
ment and safety. The inspection would obviously be incomplete, 
did it not include an examination into the causes of " wear and 
tear," and determine the extent to which it had progressed. 
Among the several causes which directly tend to rendering a 
boiler unsafe, may be mentioned the dangerous results occasioned 
by the overheating of plates, thus changing the structure of the 
iron from fine granular, or fibrous, to coarse crystalline. This 
may easily be detected by examination, and will in general be 
found to occur in such cases where the boilers are too small for 
the work, are fired too hard, or have a considerable accumulation 
of scale or sediment in contact with the plates. Blistered plates 
are almost instantly detected at sight, so also is corrosion, from 
whatever cause it may have proceeded. 

Corrosion of boiler plates* — Iron will corrode rapidly when 
subjected to the intermittent action of moisture and dryness. 
Land boilers are less subject to corrosion than marine boilers. 
The corrosion of a boiler may be either external or internal. Ex- 



446 HANDBOOK ON ENGINEERING. 



• carefully 



ternal corrosion may, in general, be easily prevented by i 
caulking all leaks in the boiler ; by preventing the dropping of 
water on the plates, such, for example, as from a leaky joint in 
the steam pipe or from the safety valve. A leaky roof, by allow- 
ing a continual or occasional dropping of water on the top of a 
boiler, especially if the boiler is not in constant use, would pro- 
mote external corrosion. Sometimes external corrosion is caused 
by the use of coal having sulphur in it, "and acts in this way : The 
sulphur passes off from the fire as sulphurous oxide, which often 
attaches to the sides of a boiler ; so long as this is dry no especial 
mischief is done ; but if it comes in contact with a wet plate the 
sulphurous oxide is converted into sulphuric acid over so much 
of the surface as the moisture extends; this acid attacks, and 
will, in time, entirely destroy the boiler plate. Internal corrosion 
is not so easily accounted for and is very difficult to correct, 
especially when it occurs above the water line. It is generally 
believed to be due to the action of acids in the feed water. 
Marine boilers are especially subject to internal corrosion when 
used in connection with surface condensers. A few years ago it 
was generally supposed to be due to galvanic action but that idea 
is now almost entirely given up. From the fact that boilers using 
distilled water fed into them from surface condensers are more 
liable to internal corrosion than other boilers, has led to the theory 
that it is the pure water that does the mischief, and that a water 
containing in slight degree a scale-forming salt, is to be preferred 
to water which is absolutely pure. Whatever may be the truth or 
falsity of this theory, it is a well established fact that distilled 
water has a most pernicious action on various metals, especially 
on steel, lead and iron. This action is attributed to its peculiar 
property, as compared with ordinary water, of dissolving free 
carbonic acid. One of the worst features in connection with 
internal corrosion is that its progress cannot be easily traced on 
account of the boiler being closed while at work. As it does not 



HANDBOOK ON ENGINEERING; 447 

usually extend over any very great extent of surface, the ordinary 
hydraulic test fails to reveal the locality of corroded spots ; the 
hammer test, on the contrary, rarely fails to locate them, if the 
plates are much thinned by its action. 

Testing boilers* — It is the general practice to apply the 
hydraulic test to all new steam boilers at the place of manufacture, 
and before shipment. The pressure employed in the test is from 
one and a half to twice the intended working steam pressure. 
This test is only valuable in bringing to notice defects which 
would escape ordinary inspection. It is not to be assumed that 
it in any way assures good workmanship, or material, or good 
design, or proper proportions ; it simply shows that the boiler 
being tested is able to withstand this pressure without leak- 
ing at the joints, or distorting the shell to an injurious degree. 
Bad workmanship may often be detected at a glance by an expe- 
rienced person. The material must be judged by the tensile 
strength and ductility of the sample tested. The design and pro- 
portions are to be judged on constructive grounds, and have little 
: or nothing in common with the hydraulic test. The great majority 
of buyers of steam boilers have but little knowledge on the sub- 
ject of tests, and too often conclude that if they have a certified 
copy of a record showing that a particular boiler withstood a test 
of say, 150 lbs., it is a good and safe boiler at 75 to 100 lbs. 
steam pressure. If the boiler is a new one and by a reputable 
maker, that may be true ; if it has been used and put upon the 
market as a second-hand boiler, it may be anything but safe at 
half the pressure named. By the hydraulic test, the braces in a 
boiler may be broken, joints strained so as to make them leak, 
bolts or pins may be sheared off, or so distorted as to be of little 
or no service in resisting steam when pressure is on. 

Hammer test* — The practice of inspecting boilers by sounding 
with a hammer is, in many respects, to be commended. It 
•equires some practical experience in order to detect blisters and 



448 HANDBOOK ON ENGINEERING. 

the wasting of plates, by sound alone. The hammer test is 
especially applicable to the thorough inspection of old boilers. It 
frequently happens in making a test that a blow of the hand 
hammer will either distort it, or be driven entirely through the 
plate ; and it is just here that the superiority of this method of 
testing over, or in connection with the hydraulic test, becomes 
fully apparent. The location of stays, joints and boiler fittings all 
modify and are apt to mislead the inspector if he depends upon 
sound alone. There is a certain spring of the hammer and a clear 
ring indicative of sound plates, which are wanting in plates much 
corroded or blistered. The presence of scale on the inside of the 
boiler has a modifying action on the sound of the plate. When a 
supposed defect is discovered, a hole should be drilled through 
the sheet by which its thickness may be determined, as well as 
its condition. 

In order to thoroughly inspect a boiler, the inspector should 
crawl into the boiler (when it is possible to do so) and he should 
look for pitting and grooving of plates, test all braces, and 
examine all inlets and outlets. 



HANDBOOK ON PJNGINEERING. 449 



CHAPTER XVII. 

USE AND ABUSE OF THE STEAM=BOILER. 

Steam-boilers* — A steam-boiler may be defined as a close 
vessel, in which steam is generated. It may assume an endless 
variety of forms, and can be constructed of various materials. 
Since the introduction of steam as a motive power a great variety 
of boilers has been designed, tried and abandoned ; while many 
others, having little or no merit as steam generators, they have 
their advocates and are still continued in use. Under such cir- 
cumstances, it is not surprising that quite a variety of opinions 
are held on the subject. This difference of opinion relates not 
only to the form of boiler best adapted to supply the greatest 
quantity of steam with the least expenditure of fuel, but also to 
the dimensions or capacity suitable for an engine of a given num- 
ber of horse-power ; and while great improvements have been 
made in the manufacture of boiler materials within the past 
fifteen years, yet the number of inferior steam-boilers seem to 
increase rather than diminish. It would be difficult to assign any 
reasonable cause for this, except that, of late years, nearly the 
whole attention of theoretical and mechanical engineers has been 
directed to the improvement and perfection of the steam-engine, 
and practical engineers, following the example set by the leaders, 
devote their energies to the same object. This is to be regretted, 
as the construction and application of the steam-boiler, like the 
steam-engine, is deserving of the most thorough and scien- 
tific study, as on the basis of its employment rest some 
of the most important interests of civilization. Until quite 
recently, the idea was very generally entertained that the 
durely mechanical skill required to enable a person to join 

29 



450 HANDBOOK OX ENGINEERING. 

together pieces of metal, and thereby f orm * a steam-tight and 
water-tight vessel of given dimensions, to be used for the gen- 
eration of steam to work an engine, was all that was needed ; 
experience has shown, however, that this is but a small portion oi 
the knowledge that should be possessed by persons who turn their 
attention to the design and construction of steam-boilers, as the 
knowledge wanted for this end is of a scientific as well as of a 
mechanical nature. As the boiler is the source of power and the 
place where the power to be applied is first generated, and alsc 
the source from which the most dangerous consequences may arise 
from neglect or ignorance, it should attract the special attention 
of the designing and mechanical engineer, as it is well known 
that from the hour it is set to work, it is acted upon by destroy- 
ing forces, more or less uncontrollable in their work of destruc- 
tion. These forces may be distinguished as chemical and 
mechanical. In most cases they operate independently, though 
they are frequently found acting conjointly in bringing about the 
destruction of the boiler, which will be more or less rapid accord- 
ing to circumstances of design, construction, quality of material, 
management, etc. The causes which most affect the integrity of 
boilers and limit their usefulness are either inherent in the mate- 
rial, or due to a want of skill in their construction and manage- 
ment ; they may be enumerated as follows : — 

First, inferior material; second, slag, sand or cinders being 
rolled into the iron ; third, want of lamination in the sheets ; 
fourth, the overstretching of the fiber of the plate on one side and 
puckering on the other in the process of rolling, to form the circle 
for the shell of a boiler ; fifth, injuries done the plate in the pro- 
cess of punching; sixth, damage induced by the use of the drift- 
pin; seventh, carelessness in rolling the sheets to form the shell, 
as a result of which the seams, instead of fitting each other 
exactly, have in many instances to be drawn together by bolts, 
which aggravates the evils of expansion and contraction when the 



HANDBOOK ON ENGINEERINGS 451 

boiler is in use ; eighth, injury done the plates by a want of skill 
in the use of the hammer in the process of hand-riveting ; ninth, 
damage done in the process of calking. 

Other causes of deterioration are unequal expansion and con- 
traction, resulting from a want of skill in setting ; grooving in the 
vicinity of the seams ; internal and external corrosion ; blowing 
out the boiler when under a high pressure and filling it again with 
cold water when hot ; allowing the fire to burn too rapidly after 
starting, when the boiler is cold ; ignorance of the use of the pick 
in the process of scaling and cleaning ; incapacity of the safety- 
valve ; excessive firing ; urging or taxing the boiler beyond its 
safe and easy working capacity ; allowing the water to become 
low, and thus causing undue expansion ; deposits of scale accum- 
ulating on the parts exposed to the direct action of the fire, 
thereby burning or crystallizing the sheets or shell ; wasting of the 
material by leakage and corrosion ; bad design and construction 
of the different parts ; inferior workjnanship and ignorance in the 
care and management. All these tend with unerring certainty to 
limit the age and safety of steam boilers. On account of want of 
skill on the part of the designer and avarice on the part of the 
manufacturer, or perhaps both reasons, boilers are sometimes so 
constructed as to bring a riveted seam directly over the fire, the 
result of which is that in consequence of one lap covering the 
other, the water is prevented from getting to the one nearest the 
fire, for which reason the lap nearest the fire becomes hotter and 
expands to a much greater extent than any other part of the 
plate ; and its constant unequal expansion and contraction, as 
the boiler becomes alternately hot and cold, inevitably results in a 
crack. Such blunders are aggravated by the scale and sediment 
being retained on the inside, between the heads of the rivets, 
which should be properly removed in cleaning. 

The tendency of manufacturers to work boilers beyond their 
capacity, especially when business is driving, is too great in this 



452 HANDBOOK ON ENGINEERING. 

country ; and no doubt many boiler explosions may be attributed 
to this cause. Boilers are bought, adapted to the wants of the 
manufactory at the time, but, as business increases, machinery 
is added to supply the demand for goods, until the engine is 
overtasked, the boiler strained and rendered positively danger- 
ous. Then again, it not unfrequently occurs that engines in 
manufactories are taken out and replaced by those of increased 
power, while the boilers used with the old engine are retained in 
place, with more or less cleaning and patching, as the case may 
require. Now, it is evident to any practical mind that boilers 
constructed for a twenty-horse power engine are ill adapted to 
an engine of forty-horse power, more especially if those boilers 
have been used for a number of years. In order to supply 
sufficient steam for the new engine, with a cylinder of increased 
capacity, the boiler must be worked beyond its safe working- 
pressure, consequently excessive heating and pressure greatly 
weaken it and endanger the lives of those employed in the vicinity. 
The danger and impracticability of using boilers with too 
limited steam-room may be explained thus : Suppose the entire 
steam-room in a boiler to be six cubic feet, and the contents of 
the cylinder which it supplies to be two cubic feet ; then at each 
stroke of the piston one-third of all the steam in the boilers is 
discharged, and consequently, one- third of the pressure on the 
surface of the water before that stroke is relieved; hence, it will 
be seen that excessive fires must be kept up in order to generate 
steam of sufficiently high temperature and pressure to supply the 
demand. The result is that the boilers are strained and burned. 
Such economy in boiler power, is exceedingly expensive in fuel, 
to say nothing of the danger. Excessive firing distorts the lire- 
sheets, causing leakage, undue and unequal expansion and con- 
traction, fractures, and the consequent evils arising from external 
corrosion. Excessive pressure arises generally from a desire on 
the part of the steam-user to make a boiler do double the work for 



HANDBOOK ON ENGINEERING. 



456 



which it was originally intended. A boiler that is constructed to 
work safely at from fifty to sixty pounds was never intended to 
run at eighty and ninety pounds ; more especially if it had been 
in use for several years. Boilers deteriorated by age should have 
their pressure decreased, rather than increased. 

One of the first things that should be, done in manufacturing 
establishments would be to provide sufficient boiler power and, in 
order to do this, the work to be done ought to be accurately cal- 
culated and the engine and boilers adapted to the results of this 
calculation. Steam users themselves are frequently to blame for 
the annoyances and dangers arising from unsafe boilers and those 
of insufficient capacity. From motives of false economy they are 
too easily swayed in favor of the cheaper article, simply because 
it is cheap, when they should consider they are purchasing an 
article which, of almost all others, should be made in the most 
thorough manner and of the best material. In view of the fearful 
explosions that occur from time to time, every steam user should 
secure for his use the best and safest. The object of a few 
dollars as between the work of a good, responsible maker and 
that of an irresponsible one, should not for one moment be 
entertained . 

It is very bad policy for steam-users to advertise for estimates 
for steam-boilers, or to inform all the boiler-makers in the town 
or city that a boiler or boilers to supply steam for an engine of a 
certain size is needed, because in this way steam-users frequently 
find themselves in the hands of needy persons, who, in their 
anxiety to get an order, will sometimes ask less for a boiler than 
they can actually make it for ; consequently, they have to cheat 
in the material, in the workmanship, in the heating-surface and in 
the fittings. As a result, the boiler is not only a continual source 
of annoyance, but, in many instances, an actual source of danger. 
The most prudent course, and in fact the only one that may be 
expected to give satisfaction, is to contract with some responsible 



454 HANDBOOK ON ENGINEERING. 

manufacturer that has an established reputation for honesty, 
capability and fair dealing, and who will not allow himself to be 
brought in competition with irresponsible parties for the purpose 
of selling a boiler. There are thousands of boilers designed, con- 
structed and set up in such a manner as to render it utterly 
imjiossible to examine, clean or repair them. Generally, in such 
cases, in consequence of imperfect circulation, the water is 
expelled from the surface of the iron at the points where the 
extreme heat from the furnace impinges, and, as a result, the 
plates become overheated and bulge outward, which aggravates 
the evil, as the hollow formed by the bulge becomes a receptacle 
for scale and sediment. By continued overheating, the parts 
become crystallized and either crack or blister ; this, if not 
attended to and remedied, will eventually end in the destruction 
of the boiler. Many boilers, to all appearance well made and of 
good material, give considerable trouble by leakage and fracture, 
owing to the severe strains of unequal expansion and contraction 
induced by the rigid construction, the result of a want of skill in 
the original design. 

DESIGN OF STEAM=BOILERS. 

It has become a general assertion on the part of writers on the 
steam-boiler that the most important object to be attained in its 
design and arrangement is thorough combustion of the fuel. 
This is only partially true as there are other conditions equally 
important, among which are strength, durability, safety, economy 
and adaptability to the particular circumstances under which it is 
to be used. However complete the combustion may be, unless 
its products can be easily and rapidly transferred to the water, 
and unless the means of escape of the steam from the surfaces on 
which it is generated is easy and direct, the boiler will fail to 
produce satisfactory results, either in point of durability or 
economy of fuel. 



HANDBOOK ON ENGINEERING. 455 

Strength means the power to sustain the internal pressure to 
which the boiler may be subjected in ordinary use, and under 
careful and intelligent management. To secure durability, the 
material must be capable of resisting the chemical action of the 
minerals contained in the water, and the boiler ought to be 
designed so as to procure the least strain under the highest state 
of expansion to which it may be subjected — be so constructed 
that all the parts will be subjected to an equal expansion, con- 
traction, push, pull and strain, and be intelligently and thoroughly 
cared for after being put in use. These objects, however, can 
only be obtained by the aid of a knowledge of the principles of 
mechanics, the strength and resistance of materials, the laws of 
expansion and contraction, the action of heat on bodies, etc. 
The economy of a steam boiler is influenced by the following con- 
ditions : cost and quantity of the material, design, character of the 
workmanship employed in its construction, space occupied, capa- 
bility of the material to resist the chemical action of the ingredi- 
ents contained in the water, the facilities it affords for the 
transmission of the heat from the furnace to the water, etc. The 
safety of any structure depends on the designer's knowledge of 
the principles of mechanics, the resistance of materials and the 
action of bodies as influenced by the elements to which they are 
exposed ; and in the case of steam bojlers, the safety depends on 
the judgment of the designer, the quality of the material, the 
character of the workmanship and the skill employed in the man- 
agement. Safety is said to be incompatible with economy, but 
this is undoubtedly a mistake, as an intelligent economy includes 
permanence and seeks durability. Adaptability to the peculiar 
purposes for which they are to be used is one of the first objects 
to be sought for in the design and construction of any class of 
machines, vessels or instruments, and it is undoubtedly this that 
gave rise to the great variety of designs, forms and modifications 
of steam boilers in use at the present day, which are, with very 



456 HANDBOOK ON ENGINEERING. 

few exceptions, the result of thought, study, investigation and 
experiment. 



FORMS OF STEAH BOILERS. 



sure 

51.11 



According- to the well-known law of hydrostatics, the pressure 
of steam in a close cylindrical vessel is exerted equally in all 
directions. In acting against the circumference of a cylinder, 
the pressure must, therefore, be regarded as radiating from the 
axis, and exerting a uniform tcnsional strain throughout the 
inclosing material. 

Familiarity with steam machinery, more especially with boil- 
ers, is apt to beget a confidence in the ignorant which is not 
founded on a knowledge of the dangers by which they are contin- 
ually surrounded ; while contact with steam, and a thoroughly 
elementary knowledge of its constituents, theory and action, only 
incline the intelligent engineer and fireman to be more cautious 
and energetic in the discharge of their duties. Many regard 
steam as an incomprehensible mystery ; and although they may 
employ it as a power to accomplish work, know little of its 
character or capabilities. Steam may be managed by common 
sense rules as well as any other power ; but if the laws which 
regulate its use are violated, it reports itself, and often in louder 
tones than is pleasant. If steam-boilers in general were better 
cared for than they are, their working age might be greatly in- 
creased. Deposits of incrustation, small leaks and slight cor- 
rosion, are too often neglected as matters of little consequence, 
but they are the forerunners of expensive repairs, delay and 
disaster. 

SETTING STEAM=BOILERS. 

While engineers differ very much in opinion respecting the best 
manner of setting boilers, they all readily allow that the results 
obtained, as regards economy of fuel and the generation of steam, 



HANDBOOK ON ENGINEERING. 457 

depend in a great measure on the arrangement of the setting. 
Particularly is this the case with horizontal tubular boilers, and 
there have been numerous plans introduced to obtain a maximum 
of steam with a minimum of fuel. Some of the most practical 
designs and best laid plans are frequently rendered useless for 
want of knowledge on the part of those whose duty it is to exe- 
cute or carry them out. This has perhaps been more frequently 
the case as regards the setting of steam boilers than any other 
class of machines, as it is customary for owners of steam boilers 
to depend too much on the knowledge of masons and bricklayers ; 
consequently, a great many blunders have been made which 
necessitated changes in the size of gratebars, alteration of brick- 
work, alteration of flues, chimney, etc., with a list of other annoy- 
ances, such as insufficiency of steam, poor draught, or something 
else. In setting or putting in boilers, all the surface possible should 
be exposed to the action of the heat of the fire, not only that the 
heat may be thus completely absorbed, but that a more equal ex- 
pansion and contraction of the structure may be obtained. Long 
boilers are often hung by means of loops riveted to the top of 
them and connected to crossbeams and arches resting on masonry 
above them, by means of hangers. This is a very mischievous 
arrangement, unless turn-buckles, or some other contrivance, are 
used to maintain a regular strain on all the hangers, as long boil- 
ers exposed to excessive heat are apt to lengthen on the lower 
side and relieve the end hangers of any weight ; consequently, 
the whole strain is transmitted to the central hanger, which has a 
tendency to draw the boiler out of shape — in many instances 
inducing excessive leakage, rupture, and, eventually, explosion. 

DEFECTS IN THE CONSTRUCTION OF STEAM BOILERS. 

The following cuts illustrate some of the mechanical defects 
that impair the strength and limit the safety and durability of 



458 



HANDBOOK ON ENGINEERING. 



steam boilers. All punched" holes are conical, and unless the 
sheets are reversed after being punched, so as to bring the 
small sides of the holes together, it will be impossible to fill them | 
with the rivets. Fig. 1 shows the position of the rivet in the 
hole without the sheets being reversed ; and it will be observed 
that, as very little of the rivet bears against the material, the ex- 
pansion and contraction of the boiler have a tendency to work it 
loose. It is apparent that such a seam would not possess over 
one-third the strength that it would if . the holes in the sheets 



Fig. 1. 





Fig. 2. 





Fig. 4. 



Fig 




Fig. 6. 



were reversed and thoroughly filled: with the rivet, as shown in 
Fig. 2. Fig. o represents what is known in boiler-making as a, 
blind-hole, which means that the holes do not come opposite 
each other when the seams are placed together for the purpose of 
rivetino-. Fig. 4 shows the position of the rivet in the blind-hole 
after beino- driven. It will be observed that the heads of the 
rivet, in consequence of its oblique position in the hole, bear only 
on one side, and that even the bearing is very limited, and 
through the expansion and contraction of the boiler, is liable to 



HANDBOOK ON ENGINEERING. 459 

work loose and become leaky. Such a seam would be actually 
weaker than that represented in Fig. 1. Fig. 5 shows the metal 
distressed and puckered on each side of the blind-hole in the 
sheets, which is the result of efforts on the part of the boiler- 
maker, by the use of the drift-pin, to make the holes correspond 
for the purpose of inserting the rivet. Fig. G shows the metal 
broken through by the same means. Now, it will be observed 
that nearly all the above defects are the result of ignorance and 
carelessness, showing a want of skill in laying out the work, as 
well as a want of proper appliances for that purpose. The evils 
arising from such defects are greatly aggravated by the fact that 
they are all concealed, frequently defying the closest scrutiny, and 
are only revealed by those forces which unceasingly act on boilers 
when in use. Such pernicious mechanical blunders ought to be 
condemned , as they are always the forerunners of destruction 
and death. There can be no reason why boilers should not be 
constructed with the same degree of accuracy, judgment and skill 
as is considered so essential for all other classes of machinery. 

IMPROVEMENTS IN STEAM=BOILERS. 

Until quite recently the steam boiler has undergone very little 
improvement. This arose, perhaps, from the fact that men of 
intelligence and mechanical genius directed their thoughts and 
labors to something more inviting and less laborious than the 
construction of steam boilers. Consequently, that branch of 
mechanics was left almost entirely to a class of men that had not 
the genius to rise in their profession or improve much in anything 
they attempted. As a result ignorance, stupidity and a kind of 
brute force were the predominant requirements in the construc- 
tion of the steam boiler ; but within the past few years this state 
of things has been changed, as some very important improvements 
have been made, not only in the manufacture of the material of 
which boilers are made, but also in the mode of constructing 



460 HANDBOOK ON ENGINEERING. 

them. The imposing, powerful and accurate boiler machinery in 
use at the present time is an evidence that the attention of emi- 
nent mechanics and manufacturers is directed to the steam boiler, 
and that in the future its improvement will keep pace with that of 
the steam engine. 

Boiler-plate is now rolled of sufficient dimensions to form the 
rings for boilers of any diameter with only one seam, obviating 
the necessity of bringing riveted seams in contact with the fire, 
as was usually the case in former times. In the manner of laying 
off the holes for the rivets, accurate steel gauges have taken the 
place of the old-fashioned wooden templet, thereby removing the 
evils induced by blind-holes, and obviating the necessity of using 
the drift-pin. So, also, in the method of bending the sheets to 
form the requisite circle — with a better class of machinery, the 
work is now more accurately performed. The old process of chip- 
ping is, in nearly all the large boiler-shops, superseded by planing 
the bevels on the edge of the sheet, preparatory to calking. Recent 
improvements in " calking" have resulted in perfect immunity from 
the injuries formerly inflicted on boilers in that process. 
In most establishments of any repute in this countiy, riveting is 
done by machinery, which is (as is well known to all intelligent 
mechanics) very much superior to hand-riveting. It is only 
small shops that enter into rivalry to secure orders and build 
cheap boilers, using poor material and an inferior quality of 
mechanical skill, that use the same old crude appliances — in 
many cases the merest makeshifts — that were in use a quarter of 
a century ago, and constructed without regard to any of the rules 
of design that are considered so essential in appliances for the 
construction of all other classes of machinery. Every engineer 
should inform himself on the subject of the safe working pressure 
of boilers, and when he finds the limit of safety has been reached, 
he should promptly inform his employer and use his influence to 
have the boiler worked within the bounds of safety. 



HANDBOOK ON ENGINEERING. 461 

To find the heating surface of a water tube boiler : — 

Rule* — Add the combined outside area of the tubes in square 
feet to one-half the area of the shell of the steam drum in square 
feet and the sum will give the total heating surface „ 

Example i. — What is the heating surface of a water tube 
boiler having fifty tubes, each three inches outside diameter and 
fifteen feet long, and the steam drum thirty-two inches in 
diameter and fifteen feet long ? 

Operation* — 3 X 3.1416 equals 9.4248 inches, the circumfer- 
ence of one tube. 15 X 12 equals 180 inches the length of one 

9.4248 X 180 
tube. YIJ. equals 11.781 square feet in one tube, and 

11.781 X 50 equals 589.05 square feet of heating surface in fifty 

32X3.1416 
tubes. Then, 1-~ equals 8.3776 linear feet the circum- 
ference of the steam drum and 8.3776 X 15 equals 125.664 square 

125.664 
feet of heating surface in steam drum, and ~ equals 62.832 

square feet, half the heating surface of steam drum. 

Then, 589.05 plus 62.832 equals 651.882 square feet, the total 
heating surface. Answer. 



STRENGTH OF RIVETED SEAHS. 

The strength of a riveted seam depends very much upon the 
arrangement and proportion of the rivets ; but with the best 
design and construction, the seams are always weaker than the 
solid plate, as it is always necessary to cut away a part of 
the plate for the rivet holes, which weakens the holes in three 
ways : 1st, by lessening the amount of material to resist the 
strains ; 2d, by weakening that left between the holes ; 3d, by 
disturbing the uniformity of the distribution of the strains. 



4<)2 HANDBOOK ON ENGINEERING. 

COMPARATIVE STRENGTH OF SINGLE AND DOUBLE 
RIVETED SEAMS. 

On comparing the strength of plates with riveted joints, it will 
be necessary to examine the sectional areas taken in a line through 
the rivet-holes, with the section of the plates themselves. It is 
obvious that in perforating a line of holes along the edge of a 
plate, we must reduce its strength. It is also clear that the plate 
so perforated will be to the plate itself nearly as the areas of their 
respective sections, with a small deduction for the irregularities 
of the pressure of the rivets upon the plate ; or, in other words, 
the joint will be reduced in strength somewhat more than in the 
ratio of its section through that line to the solid section of the 
plate. It is also evident that the rivets cannot add to the strength 
of the plates, their object being to keep the two surfaces of the 
lap in contact. When this great deterioration of strength at the 
joint is taken into account, it cannot but be of the greatest 
importance that in structures subject to such violent strains as 
boilers, the strongest method of riveting should be adopted. To 
ascertain this, a long series of experiments was undertaken by 
Mr. Fairbairn. There are two kinds of lap-joints, single and 
double-riveted. In the early days of steam-boiler construction, 
the former were almost universally employed ; but the greater 
strength of the latter has since led to their general adoption for 
all boilers intended to sustain a high steam pressure. A riveted 
joint generally gives way either by shearing off the rivets in the 
middle of their length, or by tearing through one of the plates in 
the line of the rivets. 

In a perfect joint, the rivets should be on the point of shearing 
just as the plates were about to tear ; but, in practice, the rivets 
are usually made slightly too strong. Hence, it is an established 
rule to employ a certain number of rivets per linear foot, which 
for ordinary diameters and average thickness of plate, are about 



HANDBOOK ON ENGINEERING. 463 

six per foot or two inches from center to center ; for larger 
diameters and heavier iron, the distance between the centers 
is generally increased to, say 2-J or 2 J- inches ; but in such 
cases it is also necessary to increase the diameter of the rivet, 
for while |, or even J inch rivets will answer for small diameters 
and light plate, with large diameters and heavy plate, experi- 
ence has shown it to be necessary to use J to J rivets. If 
these are placed in a single row, the rivet holes so nearly 
approach each other that the strength of the plates is much 
reduced ; but if they are arranged in two lines, a greater number 
may be used, more space left between the holes and greater 
strength aud stiffness imparted to the plates at the joint. 
Taking the value of the plate before being punched, at 100, by 
punching the plate it loses 44 per cent of its strength ; and, as a 
result, single-riveted seams are equal to 56 per cent, and double- 
riveted seams to 70 per cent of the original strength of the plate. 
It has been shown by very extensive experiments at the Brooklyn 
Navy Yard, and also at the Stevens Institute of Technology, 
Hoboken, N. J., that double-riveted seams are from 16 to 20 per 
cent stronger than single-riveted seams — the material and work- 
manship being the same in both cases : 

Taking the strength of the plate at 100 

The strength of the double-riveted joint would then be . 70 

The strength of the single-riveted would be 56 

To find the thickness of plates for the shell of a cylindrical 
boiler for a required safe working pressure in pounds per square 
inch : — 

Rule* — Multiply the required pressure per square inch by the 
radius of the shell in inches, and by the constant number 6 for 
single riveted side seams, and divide the last product by the 
tensile strength of the plates. For double riveted side seams use 
the constant number 5 instead of 6. 

Example i* — What should be the thickness of plates for a boiler 
60 inches in diameter, with single riveted side seams, for a work- 



464 HANDBOOK ON ENGINEERING. 

ing pressure of 125 pounds per square inch, the tensile strength 
of the plates being 60,000 pounds per square inch? 
125 X 30 X 6 
Operation. — 60~006 e( l uals -375 or 3/8 in. Answer. 

Example 2. — What should be the thickness of plates for a 
boiler 60 inches diameter, with double riveted*side seams, for a 
working pressure of 150 pounds per square inch, the tensile 
strength of plates being 60,000 pounds per square inch. 
150 X 30 X 5 

Operation. — f o 000 equals .375 or 3/8 in. Answer. 

The following formulas, equivalent to those of the British 
Board of Trade, are given for the determination of the pitch, 
distance between rows of rivets, diagonal pitch, maximum pitch, 
and distance from centers of rivets to edge of lap of single and 
double riveted lap joints, for both iron and steel boilers: — 

Let p = greatest pitch of rivets, in inches ; 
n — number of rivets, in one pitch ; 
£>a = diagonal pitch, in inches ; 
d = diameter of rivets, in inches ; 
T — thickness of plate, in inches ; 
V= distance between rows of rivets, in inches ; 
E = distance from edge of plate to center of rivet, in inches. 

TO DETERMINE ^HE PITCH. 

Iron plates and iron rivets — 

cPX .7854 Xn 
P = 7p + d. 

Example: First, for single-riveted joint — 

Given, thickness of plate (T) = ± inch, diameter of rivet 

(d) = | inch. In this case, n = 1. Required, the pitch. 

Substituting in formula, and performing operation indicated. 

(I) 2 X -7854 X 1 
Pitch = KhJ ^— + J =2.077 inches. 



HANDBOOK ON ENGINEERING. 465 

For double-riveted joint — 

Given, £— J inch, and d = \% inch. In this case, n==2. 
Then — 

Pitch = (WX -7854X2 + 2886 . nchesi 






For steel plates and steel rivets : — 

23 X d 2 X n . . 
P = 28 XT + d ' 
Example, for single-riveted joint : Given, thickness of plate === \ 
inch, diameter of rivet == \\ inch. In this case, n = l. 
Then — 

Pitch = 23X(it)^X.7854Xl Q71 . nehes _ 

28.X i 
Example, for double-riveted joint : Given, thickness of plate == \ 
inch, diameter of rivet = J inch. n = 2. Then — 

„•-+ i 23X(J) 2 X.7854X2 , _ . . 
Pitch = 28 X£ -+5 = 2.80 inches. 

FOR DISTANCE FROM CENTER OF RIVET TO EDGE OF LAP. 

3 X d 



E-- 



2 

Example : Given, diameter of rivet (c£) =| inch ; required, the 
distance from center of rivet to edge of plate. 

E = ^^= 1.312 inches, 

for single or double riveted lap joint. 

FOR DISTANCE BETWEEN ROWS OF RIVETS. 

The distance between lines of centers of rows of rivets for 
double, chain-riveted joints ("F) should not be less than twice the 
diameter of rivet, but it is more desirable that V should not be 

less than — ■• 



466 HANDBOOK ON ENGINEERING. 

Example under latter formula: Given, diameter of rivet = 
inch, then — 

r= (4X | ) + 1 = 2.25 inches. 
For ordinary, double, zigzag -riveted joints, 



v= V_(llp + 4ri) (p + 4*)_ 



10 

Example : Given, pitch = 2.85 inches, and diameter of rivet = J 
inch, then — 



V V (11 X 2.85 + 4 X j) (2.85 + 4XI) - m . . 

V== r~ — =1.487 inches. 

DIAGONAL PITCH. 

For double, zigzag-riveted lap joint. Iron and steel. 
6p + 4d 

Example: Given, pitch = 2.85 inches, and d = ^ inch, then — - 
(6 X2.85) + (4X1) n ■ , 

MAXIMUM FITCHES FOR RIVETED LAP JOINTS. 

For single-riveted lap joints, maximum pitch =( 1.3 IX ^) + lf • 

For double-riveted lap joints, maximum pitch =(2.62 X T) + 1|. 

Example: Given a thickness of j:>late = i inch, required, the 
maximum pitch allowable. 

For single-riveted lap joint, maximum pitch = (1.31 X i) + 
If = 2.28 inches. 

For double-riveted lap joint, maximum pitch = (2.62 X J) + 
1| = 2.935 inches. 

The following tables, taken from the handbook of Thomas W. 
Traill, entitled "Boilers, Marine and Land, their Construction 



HANDBOOK ON ENGINEERING. 



46 



and Strength," may be taken for use in single and double riveted 
joints, as approximating the formulas of the British Board of 
Trade for such joints : — 

IRON PLATES AND IRON RIVETS. 

DOUBLK-RIVETKD LAP JOINTS. 











Distance between rows 








Center of 


of rivets. 


Thickness 


Diameter 


Pitch of 


rivets to 




of plates. 


of rivets. 


rivets. 


edge of 












plates. 


Zigzag 
riveting. 


Chain 
riveting. 


T 


d 

1 


i> 


E 


V 


V 


1 6 


2.272 


.937 


1.145 


1.750 


H 


2L 
32 


2.386 


.984 


1.202 


1.812 




11 
1 6 


2.500 


1.031 


1.260 


1.875 


it 


II 


2.613 


1.078 


1.317 


1.937 


1 6 


I 


2.727 


1.125 


1.374 


2.000 


\ I& 
3 2 


If 


2.826 


1.171 


1.426 


2.062 


h 


13. 
1 6 


2.886 


1.218 


1.465 


2.125 


11 
3 2 


21 
3 2 


2.948 


1.265 


1.504 


2.187 


A 


J 


3.013 


1.312 


1.544 


2.250 . 


H 


2 9 
32 


3.079 


1.359 


1.585 


2.312 


1 


li 
L6 


3.146 


1.406 


1.626 


2.375 


tt 


31 
3 2 


3.215 


1.453 


1.667 


2.437 


U 


1 


3.284 


1.500 


1.709 


2.500 


23 
3 2 


*A 


3.355 


1.546 


1.751 


2.562 


1 


1A 


3.426 


1.593 


1.794 


2.625 


If 


1A 


3.498 


1.640 


1.836 


2.687 


If 


H 


3.571 


1.687 


1.879 


2.750 


H 


*A 


3.645 


1.734 


1.923 


2.812 


I 


iA 


3.718 


1.781 


1.966 


2.875 


2J. 


*A 


3.793 


1.828 


2.009 


2.937 


ii 

1 6 


U 


3.867 


1.875 


2.053 


3.000 


31 
3 2 


iA 


3.942 


1.921 


2.096 


3.062 


1 


iA 


4.018 


1.968. 


2.140 


3-125 



468 



HANDBOOK ON ENGINEERING. 




ZIGZAG RIVETING. 




«■£* v &■§* 




6 -&- 

) O t 


E 

■i— 

V 

E 

Jl 


^ ^___ 





CHAIN RIVETING. 




*1 



jf P_ m j£jt'}. 



o -e- 



HANDBOOK ON ENGINEERING. 469 

IRON PLATES AND IRON RIVETS. 



SINGLE-RIVETED LAP JOINTS, 




Thickness of 


Diameter of 


Pitch of 


Center of rivets to 


plates. 


rivets. 


rivets. 


edge of plates. 


T 


d 


i> 


E 


1 
i 


1 


1.524 


.937 


it 


fi 


1.600 


.984 


A 


LI 

1 6 


1.676 


1.031 


ii 

32 


ft 


1.753 


1.078 


I 


1 


1.829 


1.125 


13 
3 2 


25. 

3 •£ 


1.905 


1.171 


'h 


\l 


1.981 


1.218 


M 


¥i 


2.036 


1.265 


i 


■{ 


2.077 


1.312 


££ 


?2 


2.120 


1.359 


1 6 


15 ' 
1 6 


2.164 


1.406 


y 


31 
3 2 


2.210 


1.453 


r 


1 


2.256 


1.500 


21 
32 


* 


2.304 


1.546 


II 

1 


hV 


2.352 


1.593 


H 


M% 


2.400 


1.640 


1 


u 


2.450 


1.687 


If 


1^ 


2.500 


1.734 


13 

1 fi 


1-1% 


2.550 


1.781 


3 2 


w 


2.601 


1.828 . 


1 


u 


2.652 


1.875 


If 


i& 


2.703 


1.921 


If 


iA 


2.755 


1.968 



470 HANDBOOK ON ENGINEERING. 

STEEL PLATE AND STEEL RIVETS. 

SINGLE-RIVETED LAP JOINTS. 




Thickness of 


Diameter of 


Pitch of 


Center of rivets 

to edge of 

plates. 


plates. 


rivets. 


rivets. 


T 


d 


P 


K 


h 


LI 

M 

3 2 


1.562 


1.031 


A 


1.633 


1.078 


A 


3 
4 


1.704 


1.125 


JLl 
3 2 


25. 
3 2 


1.775 


1.171 


1 


11 


1.846 


1.218 


H 


21 
3 2 


1.917 


1.265 


.1. 

1 B 


% 


1.988 


1.312 


U5l 
32 


2 9 

3 2 


2.036 


1.359 


i 


¥% 


2.071 


1.406 


11 
3 2 


3.1 
32 


2.108 


1.453 


- 9 r . 


1 


2.146 


1.500 


is. 

3 2 


I3V 


2.186 


1.546 


1 


1-1V 


2.227 


1.593 


21. 


*A 


2.269 


1.640 


II 


ii 


2.312 


1.687 


22. 

3 2 


l-3 & 2 


2.356 


1.734 


•1 


■*3 2 


2.400 


1.781 


25 
3 2 


2.445 


1.828 


il 

32 


H 


2.500 


1.875 


1A 


2.562 


1.921 


1 


*A 


2.623 


1.968 


23 

■ 3 2 


itt 


2.687 


2.015 


15 
16 


if 


2.750 


2.062 



HANDBOOK ON ENGINEEFwING. 



471 



STEEL PLATE AND STEEL RIVETS. 

DOUBLE -RIVETED LAP JOINTS. 











Distance between rows 








Center of 


of rivets. 


Thickness 


Diameter 

of rivets. 


Pitch of 
rivets. 


rivets to 
edge of 




of plates. 












plates. 


Zigzag 


Chain 




d 






riveting. 


riveting. 


T 


P 


E 


V 


V 


-h 


\\ 


2.291 


1.031 


1.187 


1.875 


3 2 


3 2 


2.395 


1.078 


1.240 


1.937 


1 


1 


2.500 


1.125 


1.295 


2.000 


13. 


25 


2.604 


1.171 


1.349 


2.062 


~16 


H 


2.708 


1.218 


1.403 


2.125 


15. 
3 2 


11 


2.803 


1 265 


1.453 


2.187 


h 


to 


2.850 


1.312 


1.487 


2.250 


12. 
3 2 


3 2 


2.900 


1.359 


1.522 


2.312 


A 


1.5. 
1 fi 


2.953 


1.406 


1.558 


2.375 


3 L f 


3 1 
3 2 


3.008 


1.453 


1.595 


2.437 


1 




3.064 


1.500 


1.631 


2.500 


2_L 
3 2 


1-1- 
J 32 


3.122 


1.546 


1.669 


2.562 


ti 


M 6 


3.181 


1.593 


1.707 


2.625 




iA 


3.241 


1.640 


1.745 


2.687 


4 


H 


3.302 


1.684 


1.784 


2.750 


2.5. 
3 2 


^3 2 


3.364 


1.734 


1.823 


2.812 


13. 

1 6 


1_ ¥ 


3.427 


1.781 


1.863 


2.375 


32 




3 490 


1.828 


1.902 


2.937 


1 


ii 2 


3.554 


1.875 


1.942 


3.000 


29 
3 2 


^ s 1 "? 


3.618 


1.921 


1.981 


3-062 


11 


x l 6 


3.683 


1.968 


2.021 


3.125 


3 1 
T2 


Jll- 


3.748 


2.015 


2.061 


3.187 


1 


if 


3.814 


2.062 


2.102 


3.250 



472 



HANDBOOK ON ENGINEERING. 




ZIGZAG RIVETING. 




6 -&-■ 

) o < 


E 
V 
E 







CHAIN RIVETING. 





HANDBOOK ON ENGINEERING. 473 

STRENGTH OF STAYED AND FLAT BOILER SURFACES. 

The sheets that form the sides of fire-boxes are necessarily 
exposed to a vast pressure, therefore, some expedient has to be 
devised to prevent the metal at these parts from bulging out. 
Stay-bolts are generally j)laced at a distance of 41 inches from 
center to center, all over the surface of fire-boxes, and thus the 
expansion or bulging of one side is prevented by the stiffness or 
rigidity of the other. Now, in an arrangement of this kind^ it 
becomes necessary to pay considerable attention to the tensile 
strength of the stay-bolts employed for the above purpose, since 
the ultimate strength of this part of the boiler is now transferred 
to them, it being impossible that the boiler plates should give way 
unless the stay-bolts break in the first instance. Accordingly, 
the experiments that have been made by way of test of the 
strength of stay-bolts, possess the greatest interest for the practi- 
cal engineer. Mr. Fairb urn's experiments are particularly val- 
uable. He constructed two flat boxes, 22 inches square. The 
top and bottom plates of one were formed of \ inch copper, and 
of the other, f inch iron. There was a 2 a inch water-space to each, 
with i| inch iron-stays screwed into the plates and riveted on the 
ends. In the first box the stays were placed five inches from 
center to center, and the two boxes tested by hydraulic pressure. 
In the copper box, the sides commenced to bulge at 450 lbs. 
pressure to the sq. in. ; and at 815 lbs. pressure to the sq. in. 
the box burst, by drawing the head of one of the stays through 
the copper plate. In the second box, the stays were placed at 
4-inch centers; the bulging commenced at 515 lbs. pressure to 
the sq. in. The pressure was continually augmented up to 1,600 
lbs. The bulging between the rivets at that pressure was one- 
third of an inch ; but still no part of the iron gave way. At 
1,625 lbs. pressure the box burst, and in precisely the same way 
as in the first experiment — one of the stays drawing through the 



474 HANDBOOK ON ENGINEERING. 

iron plate and stripping the thread in plate. These experiments 
prove a number of facts of great value and importance to the 
engineer. In the first place, they show that with regard to iron 
stay-bolts, their tensile strength is at least equal to the grip of 
the plate. 

The grip of the copper bolt is evidently less. As each stay, 
in the first case, bore the pressure on an area of 5 x 5 = 25 square 
inches, and in the second on an area 4x4 = 16 sq. inches, the 
total strains borne by each stay were, for the first, 815 x 25 = 
20,375 pounds on each stay; and for the second, 1,625 x 16 = 
26,000 lbs. on each stay. These strains were less, however, than 
the tensile strength of the stays, which would be about 28,000 
lbs. The properly stayed surfaces are the strongest part of boil- 
ers, when kept in good repair. 

BOILER=STAYS. 

Advantage is usually taken of the self-supporting property of 
the cylinder and sphere, which enables them, in most cases, to be 
made sufficiently strong without the aid of stays or other support. 
But the absence of this self-sustaining property in flat surfaces 
necessitates their being strengthened by stays or other means. 
Even where a flat or slightly dished surface possesses sufficient 
strength to resist the actual pressure to which it is subjected, it is 
yet necessary to apply stays to provide against undue deflection 
or distortion, which is liable to take place to an inconvenient de- 
gree, or to result in grooving, long before the strength of plates 
or their attachments is seriously taxed. Boiler stays, in any 
case, are but substitutes for real strength of construction. They 
would be of no service applied to a sphere subject to internal 
pressure ; and the power of resistance would be exactly that of 
the metal to sustain the strain exerted upon all its parts alike. 
The manner in which stays are frequently employed renders them 
a source of weakness rather than an element of strength. When 



HANDBOOK ON ENGINEERING. 475 

the strain is direct the power of resistance of the stay is equal to 
the weight it would sustain without tearing it asunder ; but when 
the position of the stay is oblique to the point of resistance, any 
calculation of their theoretic strength or value is attended with 
certain difficulties. All boilers should be sufficiently stayed to 
insure safety, and the material of which they are made, their 
shape, strength, number, location and mode of attachment to the 
boiler, should all be duly and intelligently considered. Boiler 
stays should never be subjected to a strain of more than one- 
eighth of their breaking strength. The strength of boiler stays 
may be calculated by multiplying the area in inches between the 
stays by the pressure in pounds per square inch. 

Rule for finding the strain allowed on a diagonal boiler head 
brace or stay ; also rule for finding the number of stays required 
for a certain size crown sheet. 

A — Iron stays should not be subjected to a greater stress than 
from 7,000 to 9,000 pounds per square inch of section, and if 
they are located obliquely, the diameter will need to be increased 
an amount that depends on the angle of the stay to the shell. 
Find the area in square inches to be supported by the stay, and 
multiply it by the pressure per square inch, multiply the product 
by the length of the diagonal stay, and divide the result by the 
perpendicular length from the flat surface to the end of the stay. 
The quotient will be the stress on the stay, and to obtain the 
diameter 'divide the stress by the allowable stress per square inch 

of section, and the quotient 
by .7854. The square root of 
the last quotient will be the 
diameter of the stay. 

Thus, in the accompanying 
diagram, we wish to find the 
diameter of the diagonal stay 
-1, which supports an area 6" x 8" or 48 square inches. The 




476 HANDBOOK ON ENGINEERING. 

length of the stay is 25", and the perpendicular" distance be- 
tween the stayed surface and the end of the stay is 24.148". 
The boiler pressure is 100 pounds gauge, so that the 
pressure on the surface supported will be 48 x 100 or 4,800 
pounds. We multiply 4,800 by 25 and divide the product by 
24.148", which gives 4,970, nearly. The quotient of 4,970, 
divided by 7,000 equals .71; .71, divided by .7854 equals 
.9039, and the square root of this is .95 or .95", the diameter of 
a stay that will support 48 square inches in the position shown. 

A convenient formula for finding the diameter of oblique stays 
is, 

\£cosi3 

I) equals diameter of the stay. 

A " area in square inches to be supported. 

P " pressure per square inch. 

L " safe load per square inch of stay section. 

B " angle between the shell and the stay. 

Using the preceding problem as an example and referring to 
the same diagram, we have angle B equal to 15°, and ail the other 
dimensions as previously given. Therefore, 



D equals 1. 



i i ■ iQ I 48 X 100 
D equals l.lo A — 

\ 7C 



7000 X .96593 

The diameter of the stay, when the above is simplified, is 
.9526", or practically 1". A rule for finding the pitch of stays 
for any flat surface is given below. 

t. A safe formula for the strength of stayed flat surfaces is 
that given by Unwin's machine design. When the spacing of 
the stays is desired, assuming that it is the same in each direc- 
tion, we have, 



i equals 3 / J 

\2 P 



HANDBOOK ON ENGINEERING. 477 

where a equals spacing of stays or rivets in inches,/ equals safe 
working strength of the plate, t equals thickness of plate, and p 
equals boiler pressure. Expressed as a rule, this reads: Divide 
the safe strength of the plate by twice the pressure ; extract the 
square root of the quotient and multiply the final result by three 
times the thickness of the plate. The result will be the spacing 
of the stays in inches. For example, boiler pressure 100 pounds, 
plate 1/2 inch thick, safe strength of plate, 10,000 pounds per 
square inch ; 2p equals 2 x 100 equals 200 ; f/2p equals 10000/200 
equals 50; V 50 equals 7.07; ot equals 3/2 equals 1-1/2 equals 
1.5; 7.07 x 1.5 equals 10.6 for the spacing. In making such a 
calculation care must be exercised not to assume too high values 
for the strength of the plate. It is not safe to count on more 
than GO, 000 pounds for the strength of steel plates and 40,000 
for iron. The working strength must be taken not higher than 1/6 
of this, or 10,000 for steel and 6,666 for iron, and lower values 
still would be better, say 9,000 for steel and 6,000 for iron. 

2* The safe pressure for a boiler to carry, so far as the 
fiat, stayed surfaces are concerned, may be found from the 
above formula by transposing it a little, as follows : — 

9 t\f 
p equals ^ a 2 

Now, applying this, to the above example, Ave have p equals 
9x.5 2 xl0000 '■. , , 9 x. 25x10000 



which equals — — — ^ . _ ._, — and which after re- 
2x110.25 2x110.25 

22500 
duction equals equals 102, or substantially the pressure 

220.00 

assumed in the first example. 

RIVETED AND LAP WELDED FLUES. 

The following table shall include all riveted and lap- welded 
flues exceeding 6 inches in diameter and not exceeding 40 inches 
in diameter not otherwise provided by law, as required by U. S. Gov. 



478 



HANDBOOK ON ENGINEERING. 



■4- 
O 


: co I 

3 5' 

- 3" 


A COOS 


.18-inch.. 
.19-inch.. 
.20-lnch.. 
.21-inch.. 
.22 -inch.. 
.23-inch.. 
.24 inch.. 
. 25-inch.. 
.26-inch.. 
.27-inch.. 
.28-inch.. 
.29-inch.. 
.30-inch.. 
.31-inch.. 
.32 -inch.. 
.33-inch.. 
•U-inch. 


Thickness of material 
required. 












. . OQTJ O 

■ • ^^^^o op g, 


Over 6 and 
not over 7 
inches. 


g 

p 

3 

a 
a 


a . 
a ►_. 

3"00 

5". 

C3 co 

s 

5" 

O to 


f 

CD 

P 

£,5' 

O 3 

iS 

* 3 
p 

p 


c 

p 

SB a 










'. '. tSWHMM 

• • oco to 00 00 


: §3§ 

. i-j CD 2 

: ?f| 


Over 7 and 
not over 8 
inches. 










O CD CD GO GO -q ■' 
#- CO ** CD *- CD • 


■ hs a, s 
; ? ? a. 


Over 8 and 
not over 9 
inches. 


Per 
wo 








*»■ co «*■ CD tt- CO t^. . 


• H CD S 


Over 9 and 
not over 10 
inches. 


o 

3 






• j • • • ' bS^HMUMl '. 

•••••• HM«-](0(5. • 


; CD CC 3 


Over 10 and 
not over 11 
inches. 


5". 

Q to 

D" to 

3. 
p*to 

3" . 
o to 
pfca 


p 

5" 
w 

3 
CD 
OJ 

O 

3 
p 

CD 

P 

o 

p 
g 

cT 










.... OOCOOOvlMOJCn' . 

• • • • viowostDisyiorj- • 


: fi cd § 
: P?| 


Over 11 and 
not over 12 
inches. 










• • CtCtCQ0<l<IO5CnOi' • • 

• ■ en qo i— ■ m oo to C7i od k> • • • 




Over 12 and 
not over 13 
inches. 


CD 

P 








O CO CD 00 -^ -J OS tn Ol v^- • ■ • • 
tO OJ O *<■ 00 tO Ol CD CO -J ■ • • • 


: s ll 

• <-t a z 


Over 13 and 
not over 14 
inches. 


o 
t± 

P 

a 


5*. 

g. to 

O io 

io 
p*CS 

a 

is 

B. 

3 . 


CD 
3 






• C*- COCOGO bca O^OOCO 




: a*? 

lis 


Over 14 and 
not over 15 
inches. 


O 
CD 






139 
143 
150 
155 
161 
166 
171 
177 
182 
187 
193 




: 3^ 
8?| 


Over»15 and 
not over 16 
inches. 


S" 

3 

P 




• -J t>y ~q tC ij l— Oi lO OS t— OS • ■ 




i si? 

■ -s a s 

:?<f| 


Over 16 and 
not over 17 
inches. 


5 

p 

CD 




to^ito-itc-jcooowoorf^ 






: S?| 


Over 17 and 
not over 18 
inches. 


cd' 

CD 


131 
135 
140 
145 
149 
154 
159 
163 
168 
172 
176 






: gs§ 

■ >-» CD s 

: ?<f l 


Over 18 and 
not over 19 
inches. 




to 


.-~ 


O-f-O 


KWMWtO' • 






: ?<f| 


Over 19 and 
not over 20 
inches. 





HANDBOOK ON ENGINEERING. 



479 



^ 



©£ 


s 


x -o 


s . 






o ^ 


W.Q 


.d-o 




— s 


CO £ 


II 


a2 


#a 








Si 83 






5s o 


"S c 


g-3 


93^ 


'J 


J 



•saqoai 
jg J8Aoqoii 

PUTJ gg J3AQ 



•sgqoai 
ggI8AO ion 
paB 3g J8AQ 



•saqonj 
3g aaAo^oa 
pat? jg J8AQ 



•eaqoaj 
Ig aaAojou 

PUB Qg J8AQ £ A* 



•saqoai 

Og J8A0 10U 
pUB 63 J9AQ 



§ 2 8 



•saqoui 
63 aoAoioa 
paB 83 J9 a O 






•saqoui 
83 J9AO iod 
put? 12 J8AQ 



2 aa <D 



•S8qout 
£3 J9AO ion 
pUB 9g I8AQ 



§ CJ M 

S n 3 



•sgqout 
93 J8AO joa 
pat? 53 J8AQ 



2 » ^ 

3 *H 



•saqoai 
53 J8AO ?oa 
pat? f3 J» a O 

•saqoai 
f 3 J8AO }od 

pUB g£ J9AO 



•saqoai 

g3 J8AOIJOU 
puB 33 J8AQ 



■soqoai 
33 ioao ion 
paB 13 J9AQ 



•saqoai 
paB 03 J^ao 



•p8J|Tlb8I 

IBIJ83BOI jo ssaa^oiqx 



ISS 



OCOOMOSltl 






• aoMiocffnoooi- 



:2£ 



lOOSNlOOlNlOOOr 



S£S£TS!2E:'-!3t^'2 



£££££23 



3S8 



co co -<* •>* o io it, 



S-^TCCiOlOtO 



tO OS ffl t~ —< tC 



> GO a)!OiHlC05Mr-H005Mh- 






eocoeocctocofccoco^-^Tti-^cococoeow^o^ 



» o («*(N eo ^j '«s ec 



480 HANDBOOK ON ENGINEERING, 

For any flue requiring more pressure than is given in table, the 
same will be determined by proportion of thickness to any given 
pressure in table to thickness for pressure required, as per exam- 
ple : A flue not over 19 inches diameter and 3 feet long, requires 
a thickness of .39 of an inch for 176 pounds pressure; what 
thickness would be required for 250 lbs. pounds pressure? 

176: .39: : 250: .5539, 

Or a thickness of .554 inch. 

Or, if .39 inch thickness gives a pressure of 176 lbs., what will 
.554 inch thickness give? 

.39 : 176 : : .554: 250 pounds required. 

And all such flues shall be made in sections, according to their 
respective diameters, not to exceed the lengths prescribed in the 
table and such sections shall be properly fitted one into the other 
and substantially riveted, and the thickness of material required 
for any such flue of any given diameter shall in no case be less than 
the least thickness prescribed in the table for any such given 
diameter ; and all such flues may be allowed the prescribed work- 
ing steam pressure, if in the opinion of the inspectors, it is 
deemed safe to make such allowance. And inspectors are there- 
fore required, from actual measurement of each flue, to make 
such reduction from the prescribed working steam pressure for 
any material deviation in the uniformity of the thickness of the 
material, or for any material deviation in the form of the flue from 
that of a true circle, as in their judgment the safety of navigation 
may require. 

Riveted and lap-welded flues of any thickness of material, 
diameter, and length of sections prescribed in the table, may be 
made in sections of any desired length, exceeding the maximum 
length allowed by the table, by reducing the prescribed pressure 



HANDBOOK ON ENGINEERING. 481 

in proportion to the increased length of section, according to the 
following rule : — 

Rule* — Multiply the pressure in the table allowed for any pre- 
scribed thickness of material and diameter of flue by the greatest 
length, in feet, of sections allowable for such flue, and divide the 
product by the desired length of sections, in feet, from center line 
to center line of rivets, in the circular seams of such sections, and 
the quotient will give the working steam pressure allowable. 

Example* — Taking a flue in the table 24 inches in diameter, 
required to be made in sections not exceeding 2.5 feet in length, 
and having a thickness of material of .44 of an inch, and allowed 
a pressure of 157 lbs., and it is desired to make this flue in sec- 
tions 5 feet in length. 

Then we have 

1_ = 78.5 lbs. pressure allowable. 

5 

THICKNESS OF MATERIAL REQUIRED FOR TUBES AND FLUES 
NOT OTHERWISE PROVIDED FOR. 

Tubes and flues not exceeding 6 inches in diameter, and made 
of any required length ; and 

Lap-welded fines required to carry a working steam pressure not 
to exceed 60 lbs. per square inch, and having a diameter not 
exceding 16 inches, and a length not exceeding 18 feet ; and 

Lap-welded fines required to carry a steam pressure exceeding 
60 lbs. per square inch, and not exceeding 120 lbs. per square 
inch, and having a diameter not exceeding 16 inches and a 
length not exceeding '18 feet, and made in sections not exceeding 
5 feet in length, and fitted properly one into the other, and sub- 
stantially riveted ; and 

All such flues shall have a thickness of material according 
to their respective diameters, as prescribed in the following 
table : — 

31 



482 



HANDBOOK ON ENGINEERING. 



Outside 
diameter. 


Thickness. 


Outside 
diameter. 


Thickness. 


Outside 
diameter. 


Thickness. 


Inches. 


Inch. 


Inches. 


Inch. 


Inches. 


Inch. 


1 


.072 


H 


.120 


9 


.180 


H 


.072 


H 


.120 


10 


.203 


U 


.083 


3| 


.120 


11 


.220 


H 


.095 


4 


.134 


12 


.229 


2 


.095 


44 


.134 


13 


.238 


n 


.095 


5 


.148 


14 


.248 


2k 


.109 


6 


.165 


15 


.259 


n 


.109 


7 


.165 


16 


.270 


3 


.109 


8 


.165 







Tubes, water pipes and steams pipes, made of steel manufac- 
tured by the Bessemer process, may be used in any marine boiler 
when the material from which pipes are made does not contain 
more than .06 percent of phosphorus and .04 per cent of sulphur, 
to be determined by analysis by the manufacturers, verified by 
them, and copy furnished the user for each order tested ; which 
analysis shall, if deemed expedient by the Supervising Inspector- 
G-eneral, be verified by an outside test at the expense of the 
manufacturer of the tubes or pipes. No tube increased in thick- 
ness by welding one tube inside of another, shall be allowed 
for use. 

Seamless copper or brass tubes, not exceeding three-fourths of 
an inch in diameter, may be used in the construction of water 
tube pipe boilers or generators, when liquid fuel is used. There 
may also be used in their construction copper or brass steam 
drums, not exceeding 14 inches in diameter, of a thickness of 
material not less than five-eighths of an inch, and copper or brass 
steam drums 12 inches in diameter and under, having a thickness 
of material not less than one-half inch. All the tubes and drums 
referred to in this paragraph shall be made from ingots or blanks 
drawn down to size without a seam. Water-tube boilers or gen- 



HANDBOOK ON ENGINEERING. 483 

erators so constructed may be used for marine purposes with 
none other than liquid fuel. 

Lap-welded Hues not exceeding (5 inches in diameter may be 
made of any required length without being made in sections. 
And all such lap-welded Hues and riveted flues not exceeding 6 
inches in diameter may be allowed a working steam pressure not 
to exceed 225 lbs. per square inch, if deemed safe by the 
inspectors. 

Lap-welded flues exceeding 6 inches in diameter and not 
exceeding 16 inches in diameter, and not exceeding 18 feet in 
length, and required to carry a steam pressure not exceeding 
60 lbs. per square inch, shall not be required to be made in 
sections. 

Lap- welded and riveted flues exceeding 6 inches in diameter 
and not exceeding 16 inches in diameter, and not exceeding 18 
feet in length, and required to carry a steam pressure exceeding 
60 lbs. per square inch, and not exceeding 120 lbs. per square 
inch, may be allowed, if made in sections not exceeding 5 feet in 
length and properly litted one into the other, and substantially 
riveted. 

On all boilers built after July 1st, 1896, a bronze or brass- 
seated stop-cock or valve shall be attached to the boiler between 
all check valves and all steam and feed pipes and boilers, in order 
to facilitate access to connections. Where such cocks or valves 
exceed 1J inches in diameter, they must be flanged to boiler. 
The stop-valves attached to main steam-pipes may, however, be 
made of cast-iron or other suitable material. 'The date referred 
to above applies to this paragraph only. 

All copper steam-pipes shall be flanged to a depth of not less 
than four times the thickness of the material in the pipes, and all 
such flanging shall be made to a radius not to exceed the thickness 
of the material in such pipes. And all such pipes shall have a 
thickness of material according to the working steam pressure 



484 HANDBOOK ON ENGINEERING. 

allowed, and such thickness of material shall be determined by 
the following rule : — 

R u J e . — Multiply the working steam pressure in pounds per 
square inch allowed the boiler by the diameter of the pipe in 
inches, then divide the product by the constant whole number 
8000, and add .0625 to the quotient ; the sum will give the thick- 
ness of the material required. 

Example* — Let 175 lbs. = working steam pressure per square 
inch allowed the boiler, 

5 inches = diameter of the pipe, 
8000 = a constant. 
Then we have : - — 

1- .0625 = .1718 4- thickness of material in decimals of 

8000 

an inch. 

The flanges of all copper steam pipes over three inches in 
diameter shall be made of bronze or brass composition, and 
shall have a thickness of material of not less than four times 
the thickness of material in the pipes plus .25 of an inch ; and 
all such flanges shall have a boss of sufficient thickness of 
material projecting from the back of the flange a distance of 
not less than three times the thickness of material in the pipe ; 
and all such flanges shall be counter-bored in the face to lit the 
flange of the pipe ; and the joints of all copper steam pipes 
shall be made with a sufficient number of good and substantial 
bolts to make such joints at least equal in strength to all other 
parts of the pipe. ' 

The terminal and intermediate joints of all wro.ught iron and 
homogeneous steel feed and steam pipes over 2 inches in diameter 
and not over 5 inches in diameter, other than on pipe or coil 
boilers or steam generators, shall be made of wrought iron, homo- 
geneous steel, or malleable iron flanges, or equivalent material ; 
and all such llanges shall have, a depth through thy. bom of not 



HANDBOOK ON ENGINEERING. 4<Sf) 

less than that equal to one-half of the diameter of the pipe to which 
any such flange may be attached ; and such bores shall taper 
slightly outwardly toward the face of the flanges ; and the ends 
of such pipes shall be enlarged to fit the bore of the flanges, and 
they shall be substantially beaded into a recess in the face of each 
flange. But where such pipes are made of extra heavy lap-welded 
steam pipe, the flanges may be attached with screw threads ; and 
all joints in bends may be made with good and substantial 
malleable iron elbows, or equivalent material. 

All feed and steam pipes not over 2 inches in diameter may 
be attached at their terminals and intermediate joints with screw 
threads by flanges, sleeves, elbows, or union couplings; but 
where the ends of such pipes at their terminal joints are screwed 
into material in the boiler, drum or other connection having a 
thickness of not less than J inch, the flanges of such terminal 
joints may be dispensed with. 'Where any such pipes are not 
over one inch in diameter and any of the terminal ends are to be 
attached to material in the boiler or connection having a thickness 
of less than J inch, a nipple shall be firmly screwed into the 
boiler or connection against a shoulder, and such pipe shall be 
screwed firmly into such nipple. And should inspectors deem it 
necessary for safety, they may require a jam nut to be screwed 
onto the inner end oi any such nipple. 

The word ' ' terminal ' ' shall be interpreted to mean the points 
where steam or feed pipes are attached to such appliances on 
boilers, generators or engine, as are placed on such to receive 
them. 

All lap-welded iron or steel steam-pipes over 5 inches in diam- 
eter, or riveted wrought-iron or steel steam-pipes over 5 inches in 
diameter, in addition to being expanded into tapered holes and 
substantial^ beaded into recess in face of flanges, as provided in 
preceding paragraph for steam and feed-pipes exceeding 2 inches 
and nut exceeding 5 inches in diameter, shall, be substantially and 



486 



HANDBOOK ON ENGINEERING. 



firmly riveted, with good and substantial rivets, through the hubs 
of such flanges ; and no such hubs shall project from such flanges 
less than 2 inches in any case. 

Steam-pipes of iron or steel, when lap- welded by hand or 
machine, with their flanges welded on, shall be tested to a hydro- 
static pressure of at least double the working pressure of the 
steam to be carried and properly annealed after all the work 
requiring lire is finished. When an affidavit of the manufacturer 
is furnished that such test has been made and annealed, they may 
be used for marine purposes. 



WROUGHT IRON WELDED PIPE. 



GAS, 



DIMENSIONS, WEIGHTS, ETC., OF STANDARD SIZES FOR STEAM, 
WATER, OIL, ETC. 

1 inch and below are butt-welded, and tested to 300 pounds 
per square inch hydraulic pressure. 

1J inch and above are lap-welded, and tested to 500 pounds 
per square inch hydraulic pressure. 



s 

I* 


s 
a* 

SB 

o 




Length of 
Pipe per sq. 
ft. of out- | 
side surface. 


|3 




0) 
O O bc2 

§£3 3 




^ o 

o r - r 
6 ftw 

>5 


ill 
9 


Weight Of 
•Water per 
foot of 
Length. 


Inch. 


Inches. 


Inches. 


Feet. 


Inches. 


Inches. 


Feet. 


Lbs. 






Lbs. 


h 


.40 


1.272 


9.44 


.012 


.129 


2500. 


.24 


27 


.0006 


.005 


i 


.54 


1.696 


7.075 


049 


• 229 


1385. 


.42 


18 


. 0026 


.021 


I 


.67 


2.121 


5.657 


.110 


. 358 


751.5 


.56 


18 


.0057 


.047 


4 


.84 


2.652 


4 502 


.196 


.554 


472.4 


.84 


14 


.0102 


.osr, 




1 . 05 


H . 299 


3.637 


.441 


.866 


270. 


1.12 


14 


. 0230 


. 190 


i* 


1 31 


4.134 


2.903 


.785 


1 . 357 


166.9 


1.67 


114 


.0408 


.349 


11 


1 66 


5.215 


2.301 


1 227 


2 . 164 


96.25 


2.25 


114 


.0638 


.527 


l* 


1.9 


5.969 


2.01 


1.767 


2.835 


70.65 


2.69 


ill 


.0918 


.760 


2 


'2.37 


7.461 


1.611 


3.141 


4.430 


42.36 


3.66 


ll| 


. 1632 


1.356 


2| 


2.87 


9.032 


1 . 328 


4 908 


6.491 


30.11 


5.77 


8 


.2550 


2.116 


3 


3 5 


10.996 


1 091 


7.068 


9.621 


19.49 


7.54 


8 


.3673 


3.049 


H 


4. 


12.566 


.955 


9.621 


12.566 


14.56 


9.05 


8 


.4998 


4-155 


4 


4.5 


14 . 137 


. 849 


12.566 


15.904 


11.31 


10.72 


8 


.6528 


5.405 


H 


5. 


15. 70S 


.765 


15.904 


19.635 


9.03 


12,49 


8 


.8263 


6.851 


5 


5.56 


17.475 


.629 


19.635 


24.299 


7.20 


14.56 


8 


1.020 


8.500 


6 


6.62 


20.813 


.577 


28.274 


34.471 


4.98 


18.76 


8 


1.469 


12.312 


7 


7.62 


23.954 


.505 


38.484 


45.663 


3.72 


23.41 


8 


1.999 


16.662 


8 


8 62 


27.096 


.444 


50.265 


5S.426 


2.88 


28.34 


8 


2.611 


21.750 


9 


9 68 


30.433 


. 394 


63.617 


73.715 


2. 26 


34.67 


8 


3.300 


27.500 


10 


10.75 


33.772 


. 355 


78.540 


90.792 


1.80 


40.64 


8 


4.081 


34.000 



HANDBOOK ON ENGINEERING. 



487 



PULSATION IN STEAn=BOILERS. 



Pulsation in steam-boilers, though not discernible to the eye, 
as in animated nature, goes on intermittently in some boilers 
whenever they are in use. It is induced by weakness and want 
of capacity in the boiler to supply the necessary quantity of 
steam, and sometimes is caused by the boiler being badly de- 
signed, thereby admitting of a great disproportion between the 
heating-surface and steam-room. Boilers are frequently found in 
factories that were originally not more than of sufficient capacity 
to furnish the necessary quantity of steam, but, as business 
increased, it became necessary to increase the pressure and also 
the speed of the engine ; or, perhaps to replace it with a larger 
one, which has to be supplied with steam from the same boiler. 
The result is, each time the valve opens to admit steam to the 
cylinder, about one-third of the whole quantity in the boiler is 
admitted, thus lowering the pressure ; the next instant, under the 
influence of hard firing, or, perhaps, a forced draught, the steam 
is brought to the former pressure, and so on ; this lessening and 
increasing the pressure continues while the engine is in motion, 
which has an effect on the boiler similar to the breathing of an 
animal . 

The strains induced by this pulsation are transmitted to the 
weakest places, viz., the line of the rivet holes, and that marked 

by the tool in the process of 
calking ; the result is, the plate 
is broken in two, as shown in 
the above cut. The manner in 
which the break takes place 
may be illustrated by filing a 
small nick, or drilling a small 
hole, in a piece of hoop or band- 
iron, and then bending back 




488 



HANDBOOK OX ENGINEERING. 



and forth, when it will be discovered that the material will break 
just at that point, however slight the nick or small the hole may 
be. Pulsation is frequently very severe in the boilers of tug- 
boats when commencing to start a heavy tow, and also in loco- 
motives when starting long trains. Some frightful explosions of 
the boilers of tug-boats and locomotives have occurred under 
such circumstances. Pulsation, if permitted to continue, is sure 
to effect the destruction of the boiler. It is always made mani- 
fest by the vibrations of the pointers on steam gauges, or an 
unsteadiness in the mercury column. It may be remedied, to a 
certain extent, by adding a larger steam dome, but this has a 
tendency to weaken the boiler and render it more unsafe. The 
only sure preventive of such a silent and destructive agent is to 
have the boiler of sufficient capacity in the first place. 



WEIGHT OF SQUARE AND ROUND IRON PER LINEAR FOOT. 



SIDE 

OR 
DIAM. 


Weight, 


Weight, 


SIDE 

OR 

DIAM. 


Weight, 


Weight. 


SIDE 

OR 
DIAM. 


Weight, 


Weight, 


Square. 


Round. 


Square. 


Round. 


Square. 


Round. 


-1- 


.013 


.01 


2 


13.52 


10.616 


5 


84.48 


66.35 


¥ 


.053 


.041 


i 


15.263 


11.988 


4" 


93.168 


73.172 


-A- 


.118 


.093 


1 

4 


17.112 


13.44 


ft 


102.24 


80.304 


k 


.211 


.165 


1 


19.066 


14.975 


1 


111.756 


87.776 


1 


.475 


.373 


ft 


21.12 


16.588 








X 
2 


.845 


.663 


| 


23.292 


18.293 


6 


121.664 


95.552 


1 


1.32 


1.043 


4 


25.56 


20.076 


\ 


132.04 


103.704 


% 


1.901 


1.493 


I 


27.939 


21.944 


ft 


142.816 


112.16 


I 


2.588 


2.032 


3 


30.416 


23.888 


1 


154.012 


120.96 


1 


3.38 


2.654 


£ 


35.704 


28.04 


7 


165.632 


130.048 


i 


4.278 


3.359 


ft 


41.408 


32.515 


i 

4 


177.672 


139.544 


1 

4 


5.28 


4.147 


f 


47.534 


37.332 


ft 


190.136 


149.328 




6.39 


5.019 








4 


203.024 


159.456 


ft 


7.604 


5.972 


4 


54.084 


42.464 • 








1 


8.926 


7.01 


i 


61.055 


47.952 ! 


8 


216.336 


169.856 


1 


10.352 


8.128 


ft 


68.448 


53.76 








I 


11.883 


9333 


t 


76.264 


59.9 J 


9 


273.792 


215.04 



HANDBOOK ON ENGINEERING. 489 

WATER COLUriNS. 

Every boiler should be equipped with a safety water column. 
Next to keeping the steam pressure within the limits of safety, 
the most important point to be observed in operating steam boilers 
is the maintenance of the proper water level. If the water level 
is too low, there is danger of burning the tubes and plates and^ 
perhaps, of wrecking the boiler ; if it is too high, water is liable to 
be carried along with the steam and cause damage in the engine, 
while a constant variation in the water level produces a waste of fuel 
and unsteady pressure, and impairs the life of the boiler. Safety 
water columns have been devised for the purpose of insuring owners 
of steam boilers against accidents of this kind. They are so ar- 
ranged that any variation in the water level beyond reasonable lim- 
its will be loudly proclaimed by means of a suitable steam whistle. 

STEAM-GAUGES. 

The object of the steam-gauge is to indicate the steam pressure 
in the boiler, in order that it may not be increased far above that 
at which the boiler was originally considered safe ; and it is as a 
provision against this contingency that a really good gauge is a 
necessity where steam is employed, for no guide at all is vastly 
better than a false one. The most essential requisites of a good 
steam-gauge are, that it be accurately graduated, and that the 
material and workmanship be such that no sensible deterioration 
may take place in the course of its ordinary use. The pecuniary 
loss arising from any considerable fluctuation of the pressure of 
steam has never been properly considered by the proprietors of 
engines. If steam be carried too high, the suiplus will escape 
through the safety-valve, and all the fuel consumed to produce 
such excess is so much dead loss. On the other hand, if there be 
at any [time too little steam, the engine will run too slow, and 
every lathe, loom, or other machine driven by it, will lose its 
speed and, of course, its effective power in the same pro- 



490 HANDBOOK ON ENGINEERING. 

portion. A loss of one revolution in ten at once reduces the pro- 
ductive power of every machine driven by the engine ten per cent, 
and loses to the proprietor ten per cent of the time of every 
workman employed to manage such machine. In short, the loss 
of one revolution in ten diminishes the productive capacity of the 
whole concern ten per cent, so long as such reduced rate con- 
tinues ; while the expenses of conducting the shop (rent, wages ? 
insurance, etc.) all run on as if everything was in full motion. 
A variation to this amount is a matter of frequent occurrence, 
and is, indeed, unavoidable,- unless the engineer is afforded 
facilities to prevent it. A very little reflection will satisfy any 
one that it must be a very small concern, indeed, in which a half- 
hour's continuance of it would not produce a result more than 
enough to defray the cost of a very expensive instrument to pre- 
vent it. If the engineer, to avoid this loss, keeps a surplus of 
steam constantly on hand, he is constantly wasting the steam, 
and consequently, fuel, thus incurring another loss, which, 
though less alarming than the first, will yet be serious and render 
any instrument most desirable which can prevent it. It is, there- 
fore, of great importance to the proprietors of engines to have an 
instrument which can constantly indicate the pressure in the 
steam-boilers with accuracy. This would enable the engineer to 
keep his steam at a constant pressure, thus avoiding waste of fuel 
on the one hand, and the still more serious loss of the productive 
power of the shop on the other. An instrument, therefore, con- 
stantly indicating the pressure of steam, reliable in its character, 
and, with ordinary care, not subject to derangement, is evidently 
a desideratum both to the engineer and proprietor. The impor- 
tance of such an instrument, as a preventive of explosion, and of 
the frightful consequences to life and limb and ruinous pecuniary 
results of such disaster, is obvious on the slightest consideration ; 
but the value of the instrument, in the economical results of its 
daily use, is by no means properly appreciated. 



HANDBOOK ON ENGINEERING. 491 

SAFETY=VALVES. 

The form and construction of this indispensable adjunct to the 
steam boiler are of the highest importance, not only for the pres- 
ervation of life and property, which would, in the absence of that 
means of " safety " be constantly jeopardized, but also to secure 
the durability of the steam-boiler itself. And yet, judging from 
the manner in which many things called safety-valves have been 
constructed of late years, it would appear that the true principle 
by which safety is sought to be secured by this most valuable ad- 
junct is either not well understood, or is disregarded by many 
engineers and boiler-makers. 

Boiler explosions have in many cases occurred when, to all 
appearances, the safety-valves attached have been in good work- 
ing order ; and coroners' juries have not unfrequently been 
puzzled, and sometimes guided to erroneous verdicts by scientific 
evidence adduced before them, tending to show that nothing was 
wrong with the safety-valves, and that the devastating catastro- 
phies could not have resulted from overpressure, because in such 
case the safety-valve would have prevented them. It is supposed 
that a gradually increasing pressure can never take place if the 
safety-valve is rightly proportioned and in good working order. 
Upon this assumption, universally acquiesced in, when there is no 
accountable cause, explosions are attributed to the "sticking" 
of the valves, or to "bent" valve-stems, or inoperative valve- 
springs. As the safety-valve is the sole reliance, in case of neg- 
lect or inattention on the part of the engineer or fireman, it is 
important to examine its mode of working closely. Safety-valves 
are usually provided with a spindle or guide-pin, attached to the 
under side, and passing through a cross-bar within the boiler, 
directly under the seating of the valve, which may be seen in 



492 



HANDBOOK OX ENGINEERING. 



the cut below. Now, it is evident that if this guide-pin 
becomes bent from careless handling, the safety-valve may 
be rendered almost inoperative, and, instead of releasing the 
pressure at the point indicated, it will turn sideways, 
and allow only a small aperture for the escape of steam, 
and, further, it will not return perfectly to its seat; ' 
hence, a leaky valve is the result, and to overcome this difficulty, 
ignorant engineers and firemen generally resort to extra weight- 
ing ; and it is not uncommon to find double or treble the weight 




corresponding to the pressure required in the boiler. Another 
difficulty is that the safety-valve levers sometimes get bent, and 
the weight, consequently, hangs on one side of the true center ; 
this, it will be seen, causes the valve to rest more heavily on one 
side than on the other, and the greater the added w T eight the 
greater the difficulty. The seats of safety-valves should be 
examined frequently to see that no corrosion has commenced ; as 
valves, especially if leaky, become corroded and often stick fast, 
so that no little force is required to raise them. If, when a 
safety-valve is properly weighted, it should be found leaking, do 
not put on extra weights, but immediately make an examination, 
and in all probability the seat or guide-pin will be found cor- 
roded, or there will be foreign matter between the valve and its 



HANDBOOK ON ENGINEERING. 493 

seat. By taking the lever in the hand and raising it from its seat 
a few times, any substance that may have kept it from its seat 
will be dislodged ; or it may turn out on examination that the 
lever had deviated from some cause from a true center. Such 
difficulties can be easily righted, but extra weight should never be 
added, as it only aggravates the trouble instead of remedying it. 
When the weight of the safety-valve is set on the lever at safe 
working pressure, or at the distance from the fulcrum necessary 
to maintain the pressure required to work the engine, any 
extra length of lever should then be cut off as a precaution, 
to prevent the moving out of the weight on the lever, 'for the 
purpose of increasing the pressure, as, while the ' lever remains 
sufficiently long, the weight can be increased to a dangerous 
extent without attracting any attention ; while if the lever is cut 
off at the point at which the safe working pressure is designated, 
any extra increase of pressure can only be accomplished by add- 
ing more weight to the lever, which is tolerably sure to attract the 
attention of some one interested in the preservation of the lives 
and property of persons in the immediate vicinity. 

The bolts that form the connection between the lever, fulcrum 
and valve-stem should be made of brass, in order to prevent the 
possibility of corrosion, " sticking " or becoming magnetized, as 
it is termed ; and for the same reason, the valve and seat should 
be made of two different metals. When safety valves become 
leaky they should be taken out and reground on their seats, for 
which purpose pulverized glass, flour of emery, or the line grit or 
mud from grinding stone troughs are the most suitable material ; 
but whether they leak or not, they should be taken apart at least 
once a year and all the working parts cleaned, oiled and read- 
justed. The safety-valve is designed on the assumption that it 
will rise from its seat under the statical pressure in the boiler, 
when this pressure exceeds the exterior pressure on the valve, and 
that it will remain off its seat sufficiently' far to permit all the 



494 HANDBOOK ON ENGINEERING. 

steam which the boiler can produce to escape around the edges of 
the valve. The problem then to be solved is: What amount of 
opening is necessary for the free escape of the steam from the 
boiler under a given pressure? The area of a safety-valve 
is generally determined from formulae based on the velocity 
of the flow of steam under different pressures, or upon the 
results of experiments made to ascertain the area necessary for 
the escape of all the steam a boiler eould produce under a given 
pressure. But as the. fact is now generally recognized b^y 
engineers that valves do not rise appreciably from their seats 
under varying pressures, it is of importance that in practice 
the outlets round their edges should be greater than those based 
on theoretical considerations. The next point to be considered is 
how high any safety valve will rise under the influence of a given 
pressure. This question cannot be determined theoretically, but 
has been settled conclusively by Burg, of Vienna, who made 
careful experiments to determine the actual rise of safety-valves 
above their seats. His experiments show that the rise of the 
valve diminishes rapidly as the pressure increases. 

TABLE SHOWING THE RISE OF SAFETY-VALVES, IN PARTS OF AN 
INCH, AT DIFFERENT PRESSURES. 

Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. 
12 20 35 45 50 60 70 80 90 

J- JL JL JL JL JL 1_ 1_ _JL_ 
3 6 48 54 65 86 86 132 168 168 

Taking ordinary safety-valves, the average rise for pressures 
from 10 to 40 pounds is about ^l of an inch, from 40 to 70 
pounds about -gL, and from 70 to 90 pounds about T ^ of an 
inch. The following table gives the result of a series of experi- 
ments made at the Novelty Iron Works, New York, for the pur- 
pose of determining the exact area of opening necessary for 



HANDBOOK ON ENGINEERING. 



495 



safety-valves, for each square foot of heating surface, at different 
boiler pressures. 



UV 


tiA if 


*;« 


aa&o 


-_ u, 


tixi bo 














o Z * 


« ^ rt 


S o o 


© 0> ^2 


0,0 ^ 




pqcaj" 


1*1 


^ U2 & 


|sS 




a 3 

Saw 


•~"2 o 


o~<~ 


*3s 


o~<s . 


.2^3 3? 

PI o 


o^; 


v s s 


<wpi°g 


i. s a 




















3 art 


° Eu^; 


a a- 




pi Pnrt 


f&c^ 


S Pj-g 




^.25 




aj.Pj-g 




M 


^ 


* 


< 


Ph 




0.25 


.022794 


10 


.005698 


70 


.001015 


0.5 


.021164 


20 


.003221 


80 


.000892 


1 


.018515 


30 


.002244 


90 


.000796 




.014814 


40 


.001723 


100 


.000719 


3 


.012345 


50 


.001398 


150 


.000481 


4 


.010582 


60 


.001176 


200 


.000364 


5 


.009259 











TABLE OF COMPARISON BETWEEN EXPERIMENTAL RESULTS AND 
THEORETICAL FORMULAE. 



Boiler Pressure, 45 pounds. 





Area of open- 


Area of open- 


Surface. 


ing found by 
experiment! 


ing according 
to formulae. 


Sq. Ft. 


Sq. Ins. 


Sq. Ins. 


100 


.089 


.09 


200 


.180 


.19 


500 


.45 


.48 


1000 


.89 


.94 


2000 


1.78 


1.90 


5000 


4.46 


4.75 



Boiler Pressure, 75 pounds. 



Heating 
Surface 



Sq. Ft. 

100 

200 

500 
1000 
2000 
5000 



rea of open- 
ing found by 
experiment. 


Area of open- 
ing according 
to'formulae. 


Sq. Ins. 

.12 


Sq. Ins. 

.12 


.24 


.24 


.59 


.59 


1.20 


1.18 


2.40 


2.37 


6.00 


5.95 



496 HANDBOOK ON ENGINEERING. 

Now, if we compare the area of openings, according to these 
experiments, with Zeuner's formula, which is entirely theoretical, 
it will be observed that the results from the two sources are 
almost identical, or so nearly so as not to make any material 
difference. In the absence of any generally recognized rule, it 
is customary for engineers and boiler-makers to proportion safety- 
valves according to the heating surface, grate-surface, or horse- 
power of the boiler. While one allows one inch of area of 
safety-valve to 66 square feet of heating surface, another gives 
one inch area of safety-valve to every four horse power ; while a 
third proportions his by the grate-surface — it being the custom 
in such cases to allow one inch area of safety-valves to 2 square 
feet of grate-surface. This latter proportion has been proved by . 
long experience and a great number of accurate experiments, to 
be capable of admitting of a free escape of steam without allowing 
any material increase of the pressure beyond that for which the 
valve is loaded, even when the fuel is of the best quality, and the 
consumption as high as 24 pounds of coal per hour per square 
foot of grate-surface, providing, of course, that all the parts are 
in good working order. It is obvious, however, that no valve 
can act without a slight increase of pressure, as, in order to lift 
at all, the internal pressure must exceed the pressure due to the 
load . 

The lift of safety-valves, like all other puppet-valves, de- 
creases as the pressure increases ; but this seeming irregularity is 
but what might be required of an orifice to satisfy appearances in 
the liow of fluids, and maybe explained as follows: A cubic foot 
of water generated into steam at one pound pressure per square 
inch above the atmosphere, will have a volume of about 1,600 
cubic feet. Steam at this pressure will flow into the atmosphere 
with a velocity of 482 feet per second. Now, suppose the steam 
was generated in live minutes, or in 300 seconds, and the area of 
an orifice to permit its escape as fast as it is generated be re- 



HANDBOOK ON ENGINEERING. 497 

quired, 1600 divided by 482 x 300 will give the area of the orifice, 
1| square inches. If the same quantity of water be generated into 
steam at a pressure of 50 pounds above the atmosphere, it will 
possess a volume of 440 cubic feet and will flow into the atmos- 
phere with a velocity of 1791 feet per second. The area of an 
orifice, to allow this steam to escape in the same time as in the 
first case, may be found by dividing 440 by 1791x300, the 
result will be -^ square inches, or nearly J of a square inch, the 
area required. It is evident from this that a much less lift of the 
same valve will suffice to discharge the same weight of steam 
under a high pressure than under a low one, because the steam 
under a high pressure not only possesses a reduced volume, but a 
greatly increased velocity ; it is also obvious from these consider- 
ations, that a safety-valve, to discharge steam as fast as the boiler 
can generate it, should be proportioned for the lowest pressure. 

RULES. 

Rule* — For finding the weight necessary to put on a safety- 
valve lever when the area of valve, pressure, etc., are known: 
Multiply the area of valve by the pressure in pounds per square 
inch ; multiply this product by the distance of the valve from the 
fulcrum ; multiply the weight of the lever by one-half its length 
(or its center of gravity) ; then multiply the weight of valve and 
stem by their distance from the fulcrum ; add these last two prod- 
ucts together, subtract their sum from the first product, and 
divide the remainder by the length of the lever ; the quotient will 
be the weight required. 

EXAMPLE . 

Area of valve, 12 in 65 13 8 

Pressure, 65 lbs 12 16 4 

Fulcrum, 4 in. . . . . . . . . . 780 208 32 



498 HANDBOOK ON ENGINEERING. 

Length of lever, 32 in 4 13 

Weight of lever, 13 lbs. 

Weight of valve and stem, 8 lbs 3120 208 

240 32 



32)2880 240 
90 lbs. 

Rule for finding the pressure per square inch when the area of 
valve, weight of ball, etc., are known: Multiply the weight of ball 
by length of lever, and multiply the weight of lever by one-half its 
length (or its center of gravity) ; then multiply the weight of 
valve and stem by their distance from the fulcrum. Add these 
three products together. This sum, divided by the product of 
the area of valve, and its distance from the fulcrum, will give the 
pressure in pounds per square inch. 

EXAMPLE. 

Area of valve, 7 in 50 12 6 

Fulcrum, 3 in 30 15 3 

Length of lever, 30 in 1500 180 18 

Weight of lever, 12 lbs 180 

Weight of ball, 50 lbs. ........ 18 

Weight of valve and stein, 6 lbs. . . 



21)1698 3 

80.85 lbs. 21 

Rule for finding the pressure at which a safety-valve is 
weighted when the length of the lever, weight of ball, etc., are 
known: Multiply the length of lever in inches by the weight of 
ball in pounds ; then multiply the area of valve by its distance 






HANDBOOK ON ENGINEERING. 499 

from the fulcrum ; divide the former product by the latter; the 
quotient will be the pressure in pounds per square inch. 

EXAMPLE. 

Length of lever, 24 in 52 7 

Weight of ball, 52 lbs 24 8 

Fulcrum, 3 in 208 21 

Area of valve, 7 in 104 

21)1248 

59.42 lbs. 

The above rule, though very simple, cannot be said to be 
exactly correct, as it does not take into account the weight of the 
lever, valve and stem. 

Rule for finding center of gravity of taper levers for safety- 
valves : Divide the length of lever by two (2); then divide 
the length of lever by six (6), and multiply the latter quotient 
by width of large end of lever less the width of small end, 
divided by width of large end of lever plus the width of small end. 
Subtract this product from the first quotient, and the remainder 
will be the distance in inches of the center of gravity from large 
end of lever. 

EXAMPLE. 

Length of lever , . 36 in. 

Width of lever at large end 3 " 

Width of lever at small end 2 " 

36 divided by 2 = 18 minus 1.2 = 16. 8 in. 36 divided by 6 = 
6 X 1 = 6 divided by '5 = 1.2. 

Center of gravity from large end, 16.8 in. 

The safety-valve has not received that attention from engi- 
neers and inventors which its importance as a means of safety 



500 HANDBOOK ON ENGINEEKING. 

so imperatively deserves. In the construction of most other 
kinds of machinery, continual efforts have been made to secure 
and insure accuracy ; while in the case of the safety-valve, very 
little improvement has been made either in design or fitting. It 
is difficult to see why this should be so, when it is known that 
deviations from exactness, though trifling in themselves, when 
multiplied, not only affect the free action and reliability of 
machines, but frequently result in serious injury, more partic- 
ularly in the case of safety-valves. 

Safety-valves should never be made with rigid stems, as, in 
consequence of the frequent inaccuracy of the other parts, the 
valve is prevented from seating, thereby causing leakage ; as a 
remedy for which, through ignorance or want of skill, more 
weight is added on the lever, which has a tendency to bend 
the stem, thus rendering the valve a source of danger instead 
of a means of safety. The stem should, in all cases, be fitted 
to the valve with a ball and socket joint, or a tapering stem 
in a straight hole, which will admit of sufficient vibration to 
accommodate the valve to its seat. It is also advisable that 
the seats of safety-valves, or the parts that bear, should be as 
narrow as circumstances will permit, as the narrower the seat 
the less liable the valve is to leak, and the easier it is to repair 
when it becomes leaky. 

All compound or complicated safety-valves should be avoided, 
as a safety-valve is, in a certain sense, like a clock — any 
complication of its parts has a tendency to affect its reliability 
and impair its accuracy. 

It has been too much the custom heretofore for owners of steam 
boilers to disregard the advice and suggestions of their own en= 
gineers and firemen, even though men of intelligence and experi- 
ence, and to be governed entirely by the advice of self-styled 
experts and visionary theorists. 



HANDBOOK ON ENGINEERING. 501 

Table of Heating Surface in Square Feet, 



Diam. of Boiler in inches 


24 


30 


32 


34 


36 


38 


40 


42 


44 


48 


5 Heating surface of shell 
per foot of length. 


4.19 


5.24 


5.57 


5.93 


6.28 


6.63 


6.98 7.73 


7.68 


8.38 


Diameter of Tube or Flue 
in inches. 


2 


n 


3 


H 


4 


4 


5 


6 


7 


8 


Whole External Heating 
surface per foot length. 


.524 


.655 


.785 


.916 


1.05 


1.18 


1.31 


1.57 


1.83 


2.09 



50 


52 


54 


56 


58 


60 


62 


64 


QQ 


68 


70 


72 


8.73 


9.08 


9.42 


9.77 


10.12 


10.47 


10.82 


11.17 


11.52 


11.87 


12.22 


12.57 


9 


10 


11 


12 


13 


14 


15 


16 


17 


18 


19 


20 


2.36 


2.62 


2.88 


3.14 


3.40 


3.66 


3.93 


4.19 


4.45 


4.71 


4.96 


5.24 



CENTRIFUGAL FORCE. 



The centrifugal force of a body depends upon its weight IP in 
pounds ; distance R in feet it is from the center of rotation, and 
the number of revolutions N it makes about that center each 

WRN*- 

minute and equals oqqq • 

Multiply the weight in pounds by radius in feet, by square 
of number of revolutions, and divide by 2933 = centrifugal force 
in pounds. 



502 HANDBOOK ON ENGINEERING. 



CHAPTER XVIII. 
THE WATER TUBE SECTIONAL BOILER. 

The water tube sectional boiler has been a growth of many 
years and of many different minds. There are some two and a 
half million horse-power in daily service in the United States 
alone, and the number is rapidly increasing. Large orders for 
this type of boiler have often been repeated, adding proof that its 
principles are correct and appreciated by those having them in 
use and in charge. This being the case, purchasers should note 
well the points of difference in the various water tube boilers 
claiming their attention, and particularly see that the claims 
made for them are embodied in their actual construction. The 
general principles of construction and operation of this class of 
steam boilers are now well known to engineers and steam users. 
In selecting a water tube boiler there are several vital points to 
be considered : — 

1st. Straight and smooth passages through the headers of ample 
area, insuring rapid and uninterrupted circulation of the water. 

2d. The baffling of the gases (without throttling or impeding 
the circulation of the water) in such a way that they are com- 
pelled to pass over every portion of the heating surface. 

3d. Sufficient liberating surface in the steam drums to 
insure dry steam, with large body of water in reserve to draw 
from. 

4th. A steam reservoir or steam drum. 

5th. Simplicity in construction ; accessibility for cleaning and 
inspection. 

6th. A header, which in its design provides for the unequal 
expansion and contraction. 



HANDBOOK ON ENGINEERING. 



503 





Illustration above is that of a Horizontal Safety Water Tube 
Boiler, manufactured by the John O'Brien Boiler Works Company, 
of St. Louis, U. S. A. 



Down draft furnace* — A great many of these boilers are fit- 
ted with the down draft furnaces, and the above illustration shows 
the style of same, together with the manner in which they are 
connected. 

A full and complete description of these furnaces is given on 
page 522. 

Description. — In construction, this type of boiler consists 



504 HANDBOOK ON ENGINEERING. 

simply of a front and rear water leg or header, made approx- 
imately rectangular in shape, overhead combination steam and 
water drum or drums and with circulating water tubes, as 
shown in cut, which extend between and connect both front and 
rear headers, being thoroughly expanded into the tube sheets. 
The tubes are inclined on a pitch of one inch to the foot and the 
rear header being longer than the front one, the overhead drum 
connecting both headers lies perfectly level when the boiler is set 
in position. The connection of the headers with the combined 
steam and water drum is made in such a manner as to give prac- " 
tically the same area as the total area of the tubes, so there is do 
contraction of area in the course of circulation ; and extending 
between and connecting the inside faces of the water legs, 
which form end connections between these tubes and the com- 
bined steam and water drums or shells, placed above and parallel 
with them, also a steam drum above these, assures absolutely dry 
steam and a large steam space, also a large water space. The water 
legs are made larger at the top, about 11 inches wide, and at the 
bottom about 7 inches wide, which is a great advantage, allowing 
the globules of steam to pass quickly up the water legs to the 
steam and water drums. The water, as it sweeps along the 
drums, frees itself of steam ; then it goes down the back connec- 
tion until it meets the inclined tubes, meeting on its passage a 
gradually increasing temperature, till the furnace is again reached, 
where the steam formed on the way is directly carried up in the 
drum as before. The tubes extend between and connect both the 
front and rear headers and are thoroughly expanded into the 
tube sheets. Opposite the end of each tube there is an oval 
hand-hole slightly larger than, the tube" proper through which it 
can be withdrawn. It will be noted that the throat of each 
water leg is 1-J- times the total tube area. The rapid and 
unimpeded circulation tends to keep the inside surface clean and 
floats the scale-making sediment along until it reaches the back 



HANDBOOK ON ENGINEERING. 



505 



water leg, where it is carried down and settles in the bottom of leg, 
where it is blown off at regular intervals. 







mmw 




Steadiness of water leveL — The large area of surface at water 
line and the ample passages for circulation, secure a steadiness 



506 HANDBOOK ON ENGINEERING. 

of water level unsurpassed by any boiler. This is a most im- 
portant point in boiler construction and should always be consid- 
ered when comparing boilers. The water legs are stayed by hol- 
low stay-bolts of hydraulic tubing of large diameter, so placed that 
two stays support each tube and hand-hole and are subjected to only 
very slight strain. Being made of heavy material, they form the 
strongest parts of the boiler and its natural supports. The water 
legs are joined to the shell by flanged and riveted joints and the 
drum is cut away at these two points to make connection with in- 
side of water leg, the opening thus made being strengthened by 
special stays, so as to preserve the original strength. The shells 
are cylinders with heads dished to form part of a true sphere. 
The sphere is everywhere as strong as the circular seam of the 
cylinder, which is well known to be twice as strong as the side 
seam ; therefore, the heads require no stays. Both the cylinder 
and the spherical heads are, therefore, free to follow their natural 
lines of expansion when put under pressure. 

The illustration on page 505 plainly shows the formation of 
the front water leg or header in this type of water tube boiler. 

It will be seen that the hand plates are all oval in shape, allow- 
ing each one to be removed from its respective hole ; also, the 
manner of bracing with hollow stay-bolts is shown. 

Note that the feed pipes for supplying furnace are equipped 
with oval hand plates to facilitate cleaning. 

Walling in* — In setting the boiler, its front water leg is placed 
firmly on a set of strong, cast-iron columns bolted and braced to- 
gether by the door frames and dead-plates and forming the fire 
front. This is the fixed end. The rear water legs rest on rollers 
which are free to move on cast-iron plates firmly set in the ma- 
sonry of the low and solid rear wall. Thus the boiler and its walls 
are each free to move separately during expansion or contraction, 
without loosening any joints in the masonry. 

On the lower, and between the upper tubes, are placed light 



HANDBOOK ON ENGINEERING. 507 

fire-brick tiles. The lower tier extends from the front water leg 
to within a few feet of the rear one, leaving there an upward pass- 
age across the rear ends of the tubes for the flame. The upper 
tier closes into the rear water leg and extends forward to within 
a few feet of the front one, thus leaving an opening for the gases 
in front. The side tiles extend from side walls to tile bars and 
close up to the front water leg and front wall, and leave open the 
final uptake for the waste gases. 

The gases being thoroughly mingled in their passage between 
the staggered tubes, the combustion is more complete, and the 
gases impinging against the heating surface perpendicularly, in- 
stead of gliding along the same longitudinally, the absorption of 
the gas is more thorough. The draft area, being much 
larger than in fire tube boilers, gives ample time for the 
absorption of the heat of the gases before their exit to the 
chimney. 

DESCRIPTION OF THE HEINE SAFETY BOILER. 

The boiler is composed of lap-welded wrought-iron tubes ex- 
tending between and connecting the inside faces of two " water 
legs," which form the end connections between these tubes and 
a combined steam and water drum or " shell " placed above and 
parallel with them. (Boilers over 200 horse-power have two such 
shells.) These end chambers are of approximately rectangular 
shape, drawn in at top to fit the curvature of the shells. Each is 
composed of a head plate and a tube sheet flanged all around 
and joined at bottom and sides by a butt strap of same material, 
strongly riveted to both. The water legs are further stayed by 
hollow stay-bolts of hydraulic tubing of large diameter, so placed 
that two stays support each tube and hand-hole and are subjected 
to only very slight strain. Being made of heavy metal, they form 
the strongest parts of the boiler and its natural supports. The 



508 



HANDBOOK ON ENGINEERING. 



water legs are joined to the shell by flanged and riveted joints, 
and the drum is cut away at these two points to make connection 




with inside of water leg, the opening thus made being .strength- 
ened by bridges and, special stays so as to preserve the priginaj 
strength. 

48 



HANDBOOK ON ENGINEERING. 509 

The shells are cylinders with heads dished to form parts of a 
true sphere. The sphere is everywhere as strong as the circle 
seam of the cylinder, which is well known to be twice as strong as 
its side seam. Therefore, these heads require no stays. Both 
the cylinder and its -spherical heads are, therefore, free to follow 
their natural lines of expansion when put under pressure. Where 
flat heads have to be braced to the sides of the shell, both suffer 
local distortions where the feet of the braces are riveted to them, 
making the calculations of their strength fallacious. This they 
avoid entirely by their dished heads. To the bottom of the front 
head a flange is riveted, into which the feed-pipe is screwed. 
This pipe is shown in the cut with angle valve and check valve 
attached. On top of shell, near the front end, is riveted a steam 
nozzle or saddle, to which is bolted a tee. This tee carries the steam 
valve on its branch, which is made to look either to front, rear, 
right or left ; on its top the safety valve is placed. The saddle 
has an area equal to that of stop valve and safety valve combined. 
The rear-head carries a blow-off flange of about same size as the 
feed flange, and a manhead curved to fit the head, the manhole 
supported by a strengthening ring outside. On each side of the 
shell a square bar, the tile-bar, rests loosely in flat hooks riveted 
to the shell o This bar supports the side tiles, whose other ends 
rest on the side walls, thus closing the furnace or flue on top. 
The top of the tile-bar is two inches below low water line. The 
bars rise from front to rear at the rate of one inch in twelve. 
When the boiler is set, they must be exactly level, the whole 
boiler being then on an incline, i. e., with a fall of one inch in 
twelve from front to rear. It will be noted that this makes the 
height of the steam space in front about two-thirds the diam- 
eter of the shell, while at the rear the water occupies two-thirds 
of the shell, the whole contents of the drum being equally divided 
between steam and water. The importance of this will be ex- 
plained het:eafter« 



510 



HANDBOOK ON ENGINEERING, 



The tubes extend through the tube sheets, into which they are 
expanded with roller expanders ; opposite the end of each and in 
the head-plates, is placed a hand-hole of slightly larger diam- 




eter than the tube, and through which it can be withdrawn. 
These hand-holes are closed by small cast-iron hand-hole plates, 
which, by an ingenious device for locking, can be removed in a 



HANDBOOK ON ENGINEERING. 511 

few seconds to inspect or clean a tube. The accompanying cut 
shows these hand-hole plates marked H. In the upper corner 
one is shown in detail, II 1 being the top view, II 2, the side view 
of the plate itself, the shoulder showing the place for the gasket. 
H x is the yoke or crab placed outside to support the bolt and nut. 
Inside of the shell is located the mud drum 7), placed well 
below the water line, usually parallel to and 3 inches above the 
bottom of the shell. It is thus completely immersed in the hot- 
test water in the boiler. It is of oval section, slightly smaller 
than the manhole, made of strong sheet-iron with cast-iron heads. 
It is entirely inclosed except about 18 inches of its upper 
portion at the forward end, which is cut away nearly parallel to 
the water line. Its action will be explained below. The feed- 
pipe F enters it through a loose joint in front ; the blow-off pipe 
N is screwed tightly into its rear-head, and passes by a steam- 
tight joint through the rear-head of the shell. Just under the 
steam nozzle is placed a dry pan or dry pipe A. A deflection 
plate L extends from the front head of the shell, inclined up- 
wards, to some distance beyond the mouth or throat of the front 
water leg. It will be noted that the throat of each water leg is 
large enough to be the practical equivalent of the total tube area, 
and that just where it joins the shell it increases gradually in 
width by double the radius of the flange. 

Erection and walling: in* — In setting the boiler, its front 
water leg is placed firmly on a set of strong cast-iron columns, 
bolted and braced together by the door frames, dead plate, etc., 
and forming the fire front. This is the fixed end. The rear 
water leg rests on rollers, which are free to move on cast-iron 
plates firmly set in the masonry of the low and solid rear wall. 
Wherever the brickwork closes in to the boiler, broad joints are 
left which are filled in with tow or waste saturated with fireclay, 
or other refractory but pliable material. Thus the boiler and its 
walls are each free to move separately during expansion or con- 



512 HANDBOOK ON ENGINEERING. 

traction without loosening any joints in the masonry. On the 
lower, and between the upper tubes, are placed light fire-brick 
tiles. The lower tier extends from the front water leg to within 
a few feet of the rear one, leaving there an upward passage across 
the rear ends of the tubes for the flame, etc. The upper tier 
closes in to the rear water leg and extends forward to within a 
few feet of the front one, thus leaving the opening for the gases in . 
front. The side tiles extend from side walls to tile bars and close 
up to the front water leg and front wall, and leave open the final 
uptake for the waste gases over the back part of the shell, which 
is here covered above water line with a rowlock of firebrick rest- 
ing on the tile bars. The rear wall of the setting and one paral- 
lel to it arched over the shell a few feet forward, form the uptakes. 
On these and the rear portion of the side walls is placed a light 
sheet-iron hood, from which the breeching leads to the chimney. 
When an iron stack is used, this hood is stiffened by L and T 
irons so that it becomes a truss carrying the weight of such stack 
and distributing it to the side walls. 

Longitudinal section of Heine Boiler and its operation* — 
The boiler being filled to middle water line, the fire is started on 
the grate. The flame and gases pass over the bridge wall and 
under the lower tier of tiling, finding in the ample combustion 
chamber space, temperature and air supply for complete combus- 
tion, before bringing the heat in contact with the main body of the 
tubes. Then, when at its best, it rises through the spaces be- 
tween the rear ends of the tubes, between rear water leg and back 
end of the tiling, and is allowed to expand itself on the 'entire 
tube heading surface without meeting any obstruction. Ample 
space makes leisurely progress for the flames, which meet in turn 
all the tubes, lap round them, and finally reach the second uptake 
at the forward end of the top tier of tiling, with their temperature 
reduced to less than 900° Fahrenheit. This has been measured 
here, while wrought iron would melt just above the lower tubes at 



HANDBOOK ON ENGINEERING. 513 

rear etid, showing a reduction of temperature of over 1,800° Fahr. 
between the two points. As the space is studded with water 
tubes, swept clean by a positive and rapid circulation, the absorp- 
tion of this great amount of heat is explained. The gases next 
travel under the bottom and sides of shell and reach the uptake 
at just the proper temperature to produce the draft required. 
This varies, of course, according to chimney, fuel required, etc. 
With boilers running at their rated capacity, 450° Fahrenheit are 




A furnace that is used in the East a great deal. 

seldom exceeded. Meanwhile, as soon as the heat strikes the 
tubes, the circulation of the water begins. The water nearest the 
surface of the tubes becoming warmer, rises, and as the tubes are 
higher in front, this water flows towards the front water leg 
! where it rises into the shell, while colder water from the shell 
falls down the rear water leg to replace that flowing forward and 
upward through the tubes. This circulation, at first slow, in- 

33 



514 



HANDBOOK ON ENGINEERING. 



creases in speed as soon as steam begins to form. Then the 
speed with which the mingled current of steam and water rises in 
the forward water leg will depend on the difference in weight of 
this mixture, and the solid and slightly colder water falling down 
the rear water leg. The cause of its motion is exactly the same 
as that which produces'draft in a chimney. 



Plain Vertical Tubular BoAe* 




This cut shows the place for gauge cocks and water glass in an 
upright boiler. 



HANDBOOK ON ENGINEERING. 



515 




The above cut shows the water-column in its proper place. 



516 



HANDBOOK ON ENGINEERING. 



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518 



HANDBOOK ON ENGINEERING. 



2 .a «5 
0) bt«5 

o g-- 1 
© ^ 


•l^UOWippB 

iaao iad 05 


162.03 
171.10 
181.47 
194.43 
87 49 
97.99 
107.32 
116.66 
121.33 
135 32 
145.82 
153 99 
163.33 
174 99 
79 53 
89.08 
97.57 
106 06 
110.29 
123.02 
132.56 
139.99 
148.47 
159.08 
72 91 
81.66 
89 43 
97.21 
101.10 
112.77 


•aaneeaad 


135.03 
142 59 
151.23 
162.03 
72.91 
81.66 
89.44 
97 22 
101.11 
112.77 
121.52 
128.33 
136 11 
145.83 
66.28 
74.24 
81.31 
88 38 
91 91 
102.52 
110.47 
116 66 
123.73 
132 57 
60 76 
68.05 
74 63 
81.01 
84.25 
93.98 


a£co 
cu w,co 

*° s=© 

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•IBaoiiippy 
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150.45 
158 88 
168.51 
.180 55 
81.24 
90 99 
99.66 
108.32 
112.65 
125 66 
135 54 
142 99 
151 65 
162 49 
73 86 
82.71 
90.6 
98 48 
102 42 
114.24 
123.09 
129 99 
137.86 
147.72 
67.70 
75.82 
83.05 
90.26 
93.88 
104 71 


•8JTISS8IJ 


125.38 
132 4 
140.43 
150.46 
67.7 
75.83 
83 05 
90.27 
93.88 
104.72 
112.95 
119 16 
126 38 
135.41 
61.55 
68.93 
75.5 
82 07 
85.35 
95.2 
102.58 
108.33 
114.89 
123.1 
56 42 
63.19 
69 21 
75.22 
78.24 
87 26 


83 

8 rt 


•l«uoi^iDpra 
■jaao iad oz 


138.66 
146.66 
155.54 
166 65 

75 

84 

91 99 

99.99 
103.99 
115 99 
124 99 
132 

139 99 
150 

68 17 
76 35 
83.62 
90.90 
94 53 

105.44 
113.62 
120 

127.27 
136.34 
62.49 

69 99 
76 65 
83 32 
86 66 
96.66 


•ojnssajj 


115.55 
122 22 

129 62 
138.88 
62.5 
69 99 
76 66 
83.33 

86 66 
96 66 

104.18 
109 99 
116.66 
125 
66 81 
63.63 
69.69 
75.75 
78.78 

87 87 
94 69 
99.99 

106 

113.62 
52.08 
58.33 
63.88 
69.44 
72 22 
80.55 


0> 

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127.30 
134.43 
142.58 
152 77 
68.74 
76 99 
84 32 
91 65 
95.32 
106 33 
114.57 
120.99 
128.32 
137 49 
62.49 
69.99 
76 65 
83.32 
86.66 
96.66 
104.16 
109.99 
116 66 
124.99 
57.28 
64.16 
70.27 
76.38 
79.44 
88.60 


•ainssojcj 


106 09 
112.03 
118 82 
127 31 
57.29 
64 16 
70.27 
76.38 
79 44 
88.61 
95.48 
100.83 
106.94 
114.58 
52.07 
58.33 
63 88 
69.44 
72 . 22 
80^55 
86.89 
91 66 
97 22 
104.16 
47 74 
53.47 
58.56 
63.65 
66.2 
73.84 




•^aoiiTPPt! 

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115.73 
122 22 

129 62 
138.88 
62 49 
69 99 
76 65 
83.32 
86.66 
96.66 
104 16 
109.99 
116 66 
124.99 
56 8 
63.63 
69 69 
75.75 
78 78 
87.87 
94.69 
99.99 
106 05 
113.62 
52.08 
58.33 
63.88 
69.44 
72 21 
80.54 


O "U 00 
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96.44 
101 84 
108 02 
115.74 
52.08 
58.33 
63.88 
69.44 
72.22 
80.55 
86.8 
91.66 
97 22 
104.16 
47.34 
53 
58 

63.13 
65.65 
73 23 
78.91 
83.33 
88.38 
94 69 
43.4 
48.6 
53.24 
57. S7 
60.18 
67 12 


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104.16 
109.99 
116 66 
124.99 
56.24 
63 
69 
75 
78 
87 

93.74 
99 
105 
112.5 
51.13 
57.26 
62.72 
68 17 
70 9 
79.08 
85.2 
90 

95.47 
102 26 
46.87 
52.5 
57.49 
62 49 
64 99 
72.49 




36. S 

U.66 

37.22 

14.16 

16.87 

)2.5 

)7.5 

52.5 

35 

72.5 

78.12 

32 5 

37.5 

)3.75 

12 61 

17.72 

32.27 

36.81 

>9.09 

35.90 

'1 

"5 

79.56 

35 22 

39 06 

13.75 

17 91 

32.08 

54.16 

30 41 



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M«MMMiH(M(NN<N(NWWWCOrl?q(M(NM(N 



HANDBOOK ON ENGINEERING. 



519 



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520 



HANDBOOK ON ENGINEERING. 




The above cut shows the proper place for closing in the. boiler 

on the side — also the space between side of boiler 

and side walls. 



HANDBOOK ON ENGINEERING. 



521 




The above cut shows the proper place for gauge-cocks in a 
submerged tube boiler. 



522 



HANDBOOK ON ENGINEERING. 



THE AMOUNT OF MATERIAL REQUIRED TO BRICK 
UP BOILERS OF DIFFERENT SIZE. 



03 s 

.2 o 



S s 

•^ hi. 
.2^ 



^ 


HIM 


u. 






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— 


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03 



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03^ 


88 


8 


80 


8 


72 


7 


80 


7 


72 


7 


80 


6 


72 


6 


64 


6 


72 


6 


64 


5 


72 


5 


64 


4 



03 O O Oj "S 

O o • £ 



72"x22' 
72"x20' 
72"xl8' 
60"x20' 
60"xl8' 
54"x20' 
54"xl8' 
54"xl6' 
48"xl8' 
48"xl6' 
42"xl8' 
42"xl6' 



10,500 


2,500 


10,000 


2,300 


9,500 


2,200 


9,500 


2,200 


9,000 


2,000 


8,700 


1,900 


8,000 


1,800 


7-, 500 


1,700 


7,500 


1,600 


7,200 


1,500 


7,000 


1,400 


6,500 


1,300 



18 bu. 
18 bu. 
17 bu. 
17 bu. 
16 bu. 
15 bu. 
15 bu. 
14 bu. 
14 bu. 
14 bu. 
12 bu. 
12 bu. 



9bbl. 
8bbl. 
8bbl. 
8bbl. 
8bbl. 
8bbl. 
8 bbl. 
7bbl. 
7 bbl. 
7 bbl. 
7 bbl. 
7 bbl. 



If 13" wa 



The dowr 



L \ less on Red Brick. 

THE DOWN DRAUGHT FURNACE. 

draught furnace is noted for being one of the best 
smoke preventing furnaces in the market, while at the same time 
the cheapest kind of coal can be used. 

The down draught furnace made a good smoke record, even 
with overworked boilers, doing variable work, and with a marked 
economy in fuel. My experience with the down draught furnace, 
I feel safe in saying that smoke from boiler furnaces can now be 
abated by practical means, without hardship, no matter what the 
type of boiler. 

Directions for firing the Down Draught Furnace* — When 
firing the furnace, throw the coal evenly over the entire grate 
surface, from 6 to 8 inches in depth, a little heaviest at the 
rear end of the furnace. Do not put in too much coal — 
burn more air ; and economize with your fuel and 



HANDBOOK ON ENGINEERING. 



523 



do not pile up the coal in front near the door. Never fire any 
fresh coal on the lower grates ; let in air below the lower grates. 
When poking the fire, run the slice-bar down between the water 
grates and back the full length of the grates ; then raise the slice- 
bar and gently shake the coal, and then pull it out without stir- 
ring up the tire. Never turn the fire over so that black coal gets 
down upon the water grates, unless there is a large clinker to re- 
move. Never give the top grates a general cleaning, so as to 
leave a portion of the grates uncovered and the remainder with a 
hot fire on them, as this causes an uneven expansion in the differ- 
ent tubes forming the water grates, and is liable either to bend 
the tubes or strip off the threads where they enter the drums. 
When the top fire becomes clogged with clinkers so that you can- 




Down Draught Furnace. 



not keep up steam, run in the slice-bar and raise the clinkers to 
the top of the fire ; remove the large clinkers, leave the small ones 
alone, and put on afresh fire. The lower grates must have proper 



524 



HANDBOOK ON ENGINEERING. 



attention. The coals must be raked over evenly and all holes 
filled up, particular care being taken that the grates are perfectly 
covered all over. If considerable coals have accumulated on the 




View of the Down Draught Furnace. 

lower grates and the air spaces are closed with ashes or clinkers, 
the slice-bar must be used and the clinkers raised up and turned 
over and the larger ones removed. It is best to remove the clink- 
ers every two or three hours, leaving the coals to burn up. 



SPECIFICATIONS FOR ONE SIXTY=INCH HORIZONTAL 
INCH FLUE BOILER. 



SIX= 



General directions. — There will be one boiler 20 feet long from 
out to out of heads and 60 inches inside diameter. 

Material, quality, thickness, etc* — Material in shell of the 
above named boiler to be made of homogeneous flange steel T 5 g" 
thick, having a tensile strength of not less than 60,000 lbs. to 



HANDBOOK ON ENGINEERING. 



525 




52(5 HANDBOOK ON ENGINEERING. 

the square inch of section, with not less than 56 per cent ductil- 
ity, as indicated by contraction of area at point of fracture under 
test, or by an elongation of 25 per cent in length of 8 inches. 
Heads must be J" thick and of the same quality of steel as that 
in the shell. All plates and heads must be plainly stamped with 
the maker's name, and tensile strength. 

Tubes, size, number and arrangement* — The boiler must 
contain 18-6" lap-welded flues, riveted, to the heads with Ten J" 
rivets in each head ; said flues must be made of charcoal iron of the 
best American make, standard thickness, equal to the National 
Tube Works Company's make. All flues must have at least 3 
inch clear space between them, and not less than 3 inches 
between flues and shell. All flanging of heads must be free from 
flaws or cracks of any description, and properly annealed in an 
annealing oven before riveting to the boiler. If 4-inch flues are 
wanted in place of 6-inch, the boiler must have 44 best lap- 
welded tubes, 4" in diameter and 20 feet long, set in vertical and 
horizontal rows, with a clear space between them, vertically and 
horizontally of 11", except the central vertical space, which is to 
be 4 inches. Holes for tubes to be neatly chamfered off on the 
outside. Tubes to be set with a Dudgeon expander, and beaded 
down at each end. 

Riveting", — The longitudinal seams of the boiler must be 
above the fire line, and have a triple row of rivets ; all rivets to 
be |" in diameter ; and all rivets to be of sufficient length to 
form upheads equal in size to the pressed heads of same. The 
rivets in the longitudinal seams must be spaced 31" apart 
from center to center, and the rows of same to be pitched 2 T 3 g" 
apart from center to center, so as to give an efficiency of the 
joint of t 7 q 6 ¥ per cent of the solid plate. Transverse seams to 
be single riveted with same size rivets as those in the longitudinal 
seams pitched 2" apart from center to center. Care must be 
taken in punching and drilling holes that they may come fair in 



HANDBOOK ON ENGINEERING. 527 

construction; the use of adrift-pin to bring blind, or partially 
blind holes in line will be sufficient cause for the rejection of 
the boiler. 

Calking* — The edges of the plates to be planed and beveled 
before making up the boilers, and the calking to be done with 
round nose tools, pneumatically driven ; no split or wedge calk- 
ing will be allowed. 

Bracing* — There must be 22 braces in the boiler, one inch area 
at least, be nine above the flues on the front head and nine similar 
ones on the back head, none of which shall be less than 3' 6" long, 
made of good refined iron and securely riveted to the heads ; the 
other end to be extended to the shell of boiler and riveted thereto 
with two J'' rivets. Care must be exercised in the setting of 
them, so they may bear uniform tension. There must be two 
braces below flues, one on each side of manhead, and riveted to 
the heads with two J" rivets. The back end of brace to be ex- 
tended backward to side of shell and riveted thereto by means 
of two |" rivets ; and two braces in back end above flues, one 
on each side and riveted the same as the other two below 
flues. 

Manholes* — The boiler to have two manholes of the Hercules 
or Eclipse pattern, same to be of size 10"xl5", one located in 
front head, beneath the flues, and the other in rear head above 
the flues, and each to be provided with a lead gasket, grooved lid, 
two yokes and two bolts. The proportion of the whole to be 
such as will leave it as strong as any other portion of the head of 
like area. 

Steam drum. — The boiler must be provided with one steam 
drum 30" in diameter by 5' in length, shell plates of which are to 
be T 5 ¥ " thick and heads a" thick, of the same quality of material 
as that in the boiler. The heads must be bumped to a radius so 
as to give as near as practicable equal strength as to that in the 
shell without bracing. The longitudinal seams of the drum are 



528 HANDBOOK ON ENGINEERING. 

to be doubly riveted with -J-J-" diameter rivets, pitched 2 |" apart 
from center to center, so as to give an efficiency of the joint of 
To 4 o P er cen ^ °^ ^ ne s °lid plate. 

Manhole in drum. — The drum must be provided with Her- 
cules or Eclipse Patented Manhole, same to be of size 10" x 15", 
located in the center of one head, and to be provided with a 
grooved lid, lead gasket, two yokes and two bolts. The propor- 
tion of the whole to be such as will leave it as strong as any other 
portion of the head of like area. 

To attach to boilers* — The steam drum must be attached to 
the boiler by means of two flange steel connecting legs, 8" in 
diameter by 12" in length, and securely riveted to boiler and 
steam drum shell. 

Mud drum* — Boiler must be provided with one mud drum 
24" in diameter and of sufficient length so that each end may 
come flush with the outside of the boiler walls on each side ; the 
quality and thickness of steel to be the same as that specified for 
the steam drum, and all seams to be single riveted ; said mud 
drum to be provided with one Hercules or Eclipse Patent Manhole 
in one end, and to be of size 9" x 14", supplied with a grooved 
lid, lead gasket, two yokes and two bolts. 

To attach to boiler* — The mud drum is to be attached to 
boiler by means of 8" diameter steel connecting leg, about 16" in 
length, properly riveted to boiler and mud drum shells. 

Flanges. — The boiler to have one 8" wrought steel flange riv- 
eted on top of steam drum ; one wrought steel flange 4" in diam- 
eter, about 5 feet from front end of boiler for safety valve one 
2" wrought steel flange on after end of boiler over the center of 
mud leg for supply pipe — all flanges to be threaded ; 2" hole in 
mud drum for blow-off ; also 2 1J" holes, one on top of boiler 
and one on end near bottom of boiler for water column. 

Fusible plug's. — To have two fusible plugs ; one inserted in 
shell from inside on second sheet, or about 5' from forwardend, 1 



HANDBOOK ON ENGINEERING. 529 

inch above flues ; one plug inserted in top of flue, not more than 
three feet from after end. 

Trimmings* — Furnish one 4" spring or dead weight safety 
valve, 4" diameter ; one water combination column ; provide same 
with two 1J" valves for the steam and water connections between 
the boiler and column, and one ^" valve for blow-pipe ; said blow- 
pipe to be connected with ashpit ; said combination barrel to be 
4'' diameter, 18'' long, and made of cast-iron. Also, furnish one 
water gauge having a |" x 15" Scotch glass tube, bodies polished 
with wood wheels and guards, rods, bodies threaded |" ; three 
gauge cocks J" register pattern, polished brass bodies ; one steam 
gauge with 10" dial ; one 2" brass feed valve with 2" check 
valve ; one 2" globe valve for blow-off from mud drum ; also one 
asbestos packed stop-cock for same, so as to insure against the 
possibilities of a leak through the blow-pipe. Water column to 
have crosses in place of ells. Crosses to have brass plugs. 

Castings, grates, doors, etc* — The boiler must be provided 
with a heavy three-quarter fire front of neat design, having double 
firing and ashpit doors, anchor bolts for anchoring fire fronts in 
place, heavy deadplates, a full set of fire liners 9" deep for sup- 
porting firebrick on end, front and rear bearing bars ; a full set 
of ordinary grate bars 4 ft. long, soot door and frame for cleaning 
out rear ashpit ; a full set of skeleton arch plates ; 12 heavy buck 
staves 9J' long, provided with tie rods, nuts and washers, heavy 
back stand with plate and expansion rollers ; also furnish wrought 
plates to cover mud drum. 

Fire tools* — Furnish in addition to above two sets of fire tools 
consisting of two pokers, two hoes, two slice-bars, two claws, and 
one six inch flue brush with i" - pipe for handle. 

Breeching* — Boiler must have a breeching fitted to front head 
and fastened thereto by means of bolts, stays and suitable pieces 
of angle iron, bent to conform to circle of boiler. The underside 
of breeching is to run across the head between the lower flues and 

34 



530 HANDBOOK ON ENGINEERING. 

the manhole, leaving the manhole freely exposed ; the sides of 
breeching are to be made of T 3 g" steel, the front and doors of i" 
steel ; said doors to be hung by means of strap hinges, provided 
with suitable fastenings so as to give free access to all flues when 
open. 

Uptake and dampen — An uptake having an area of 1221 
square inches must be fitted to top of breeching. Said uptake 
must be of convenient form for attaching to a stack 40" in diam- 
eter and provided with a close-fitting damper having a steel hand 
attachment, so that same may be operated conveniently from the 
boiler room floor. 

Smoke stack. — There is to be provided for the above boiler 
one smoke stack 40" in diameter by 90 feet in height, half of 
which is to be made of No. 8, and the other half of No. 10 best 
black sheet steel throughout, and supplied with two sets of four 
guy rods, each consisting of |" galvanized wire cable guy strand 
with turn buckles for same. 

In general* — The above-mentioned boiler must be made of 
strictly first-class material and workmanship throughout, and sub- 
jected to a hydrostatic pressure of 150 pounds to the square inch 
before leaving the works of the manufacture. 

Painting boiler breeching* — Smoke stack and boiler front, 
steam and mud drum, and all trimmings, to have two good coats 
of coal tar. 

Masonry* — Boiler to be set in good substantial masonry, of 
hard burned brick and good mortar, made of clean, sharp sand 
and fresh burned lime. Walls to be 18" thick. The outside walls 
to be laid up of selected hard burned brick, with close joints 
struck smooth and rubbed down.. The sides, end and bridge 
walls, and boiler front, to have a foundation of 24" wide and 12' 
deep, laid in Portland cement. The ash pit to be paved with 
hard burned brick set on edge firmly, imbedded in Portland 
cement. For a distance of seven feet in front of the boiler and 



HANDBOOK ON ENGINEERING. 531 

continuing across entire width of front of boiler setting- to be 
paved with hard burned brick set on edge, firmly imbedded in 
sand. The walls to be carried up to the full height and a row- 
lock course of brick 4" thick to be carried over top of boiler from 
side wall to side wall, extending the whole length of boiler, and 
the entire arch to be plastered over on the outside with mortar. 
The bridge walls to be 24", carried up to within 6" of under 
side of boiler. The top of bridge wall to be of fire brick and 
made in the form of an inverted arch, conforming to the shell of 
the boiler. The space under boiler and back of bridge wall to 
the back end of boiler, to be filled in with earth or sand and the 
top paved with brick, and tapering from bridge w T all back to back 
end to 12" at back end, and in a similar form and shape, that is, 
inverted arch. The uptake for returning the smoke and heat at 
back end of boiler, to be arched over from rear wall against the 
back head of boiler 2" above the tubes, the arch being made of arch 
fire brick, and backed up with red brick. Furnace to be lined 
throughout with first quality fire brick, dipped in fire clay with 
close joints and fire brick rubbed to place, from a point 2" below 
grates, to where it safes in against boiler, and to be continued fire 
brick as far back as the rear end of setting and across rear end of 
same ; it being the intent that all interior surfaces of the setting 
with which the heat comes in contact, shall be faced with fire 
brick. Every sixth course to be a header course. 

Smoke connections* — The connection from boiler to chimney 
to be made of No. 12 black iron, with cleaning door and damper 
in same. 

BANKING FIRES. 

Different engineers pursue different methods in banking fires. 
One method is to push the fire back one-third towards the bridge 
wall, and clean off the grate in front. Then shovel in from 150 
to 300 lbs. of fine coal on top of the fire, closing ash-pit doors 



532 HANDBOOK ON ENGINEERING. 

and leaving furnace doors open, with damper open enough to let 
the gases escape. Others bank after this fashion but close all 
doors and air holes, leaving the damper partially open. Another 
method is to level the fire all over the grate, and shovel in from 
150 to 500 lbs. of fine coal, — depending on the size of the 
grate, — and then cover the whole surface with wet ashes to a 
good depth, so that no fire nor flame can be seen, then close the 
ash-pit doors, leaving the furnace doors ajar, and leave the 
damper partially open so that the gases may escape. In the 
morning, rake out the ashes, clean the fire, and throw in fresh 
coal. 

INSTRUCTIONS FOR BOILER ATTENDANTS. 

The following instructions apply more particularly to horizontal 
return tubular boilers, although in a general way they are appli- 
cable to all types of boilers. 

Never start a fire under a boiler until you are positively certain 
that there is sufficient water in the boiler, — at least two gauges 
of water. Do not trust to the water gauge alone, but try the 
gauge cocks also, and try them at intervals during the clay, be- 
cause the water-gauge pipe connections may be choked and cause 
a false water level. 

Before starting a fire be sure that the blow-off cock is closed 
and not leaking. 

Before it is time to start the engine, pump up three gauges of 
water, and blow off one gauge, in order to get rid of mud and 
other sediment. If the boiler has a surface blow-off, — commonly 
called a "skimmer," — blow off the scum before stopping the 
engine for the day. 

When the day's work is done, leave three gauges of water in 
the boiler, to allow for leakage and evaporation during the night. 

Never raise steam hurriedly. Sudden changes of temperature 
may produce fractures, or start leaks. 



HANDBOOK ON ENGINEERING. 533 

111 starting a fire in a furnace, a good plan is to cover the grate 
with a thin layer of coal and to place the shavings and wood on 
the coal and then light the shavings. 

The advantage of placing a covering of coal on the grate before 
the wood and shavings, is that it is a saving of fuel, as the heat 
that would be transmitted to the bars is absorbed by the coal, and 
the bars are also protected from the extreme heat of the fresh 
fire. 

Lift the safety-valve, — if of the lever pattern, — every morn- 
ing while raising steam, and satisfy yourself that it is in good 
working order, and that the pi is set at the proper point on the 
lever. The most disastrous explosions have occurred with boilers 
whose safety-valves had been stuck down or overloaded. 

Keep the boiler shell free of soot. Soot is a very good non- 
conductor of heat, and considered worse than scale inside of a 
boiler. 

Keep your boiler tubes free from soot and dust. Choked tubes 
impair the draft. The tubes should be cleaned twice a week, or 
oftener. 

Soot collects also in a stack or chimney and in the connection 
between the" breeching "and stack, and interferes with the draft. 

Open your boiler every two weeks, or, as often as necessary, — 
depending on the kind of feed-water used, — and clean out the 
mud and scale. At the same time examine all of the stays, and 
see that they are taut and in good order. Also, look for pitting 
around the mud-drum connection, and for grooving in the side 
seams. Examine all outlets and pipe connections, and look for 
indications of " bagging " in the furnace sheets. 

Clean off the fusible plugs both inside and outside of the boiler. 
A fusible plug covered with soot on the fire side, and with scale 
on the water side, is no longer a " safety plug." Renew the 
filling in safety plugs, at least once a year. They are filled with 
pure Banca tin. 



534 HANDBOOK ON ENGINEERING. 

Be perfectly satisfied that your boiler is in good condition 
internally before you close it up. 

Just as soon as you have fastened the man-head in its place, 
turn on the feed-water until you get at least three gauges of water. 
Fires have been built under empty boilers, aud will be again, if 
you forget to turn on the feed water after cleaning out. 

Do not empty a boiler while it is under steam pressure, but 
allow it to get cold before letting the water run out. 

If you are in a great hurry and can't wait for the boiler to cool 
down, nor for the brickwork or anything else to cool clown, draw 
the fire and open the furnace and ash-pit doors, then turn on the 
feed water, and from time to time blow out, until the steam gauge 
shows no pressure ; then shut .off the feed-water, raise the safety 
valve, open the blow-off cock, then open up the boiler. 

Before opening a man -hole, lift the safety-valve, so as to be 
sure that there is neither pressure nor vacuum in the boiler. 

Look well after the brick-work surrounding your boiler, and 
stop all cracks in the walls with mortar or cement, as soon as 
discovered. They impede the draft, and cool the plates of the 
boiler, causing a waste of fuel. 

See that the bridge-wall is in perfect condition, because a gap 
in the bridge wall might cause a " bag " in the boiler by concen- 
trating the flames on one spot. 

Never allow any bare places on the grate, nor any accumulation 
of ashes, or dead coal in the corners of the furnace, as such 
places admit great quantities of cold air into the furnace, and 
render the combustion very imperfect. 

In firing with anthracite coal, do not poke and stir up the fire, 
as with soft coal, but let it alone. 

In firing soft slack coal, fire very lightly but frequently, carry, 
ing a thin fire. 

In firing with soft lump coal, carry a thick fire, say from six 
to eight inches deep, according to the size of the furnace. 



HANDBOOK ON ENGINEERING. 535 

In firing up, you may spread the fresh coal evenly all over the 
; grate, or, you may push the live coals back towards the bridge- 
iwall, leaving a thin bed of live coals near the furnace doors, and 
spreading the fresh coal on top of it. This is called carrying a 
coking fire. Some prefer the one and some the other method°of 
firing. 

In case you should find the water in the boiler out of sight, 
and a heavy fire in the furnace, don't get rattled, and don't lose 
jyour head. Open the furnace doors, and close the ash-pit doors, 
and cover the fire with wet ashes, or damp clay, completely 
smothering it. Let everything else alone, including the safety 
valve and the engine. Now wait until the boiler cools down and 
the gauge shows no pressure, then turn on the feed-water. 

On the other hand, if there is but very little fire in the furnace, 
you may draw the fire, instead of covering it with ashes or clay.' 

If your boiler foams badly, and you are uncertain as to the 
jwater level, stop the engine, and the true water level will show 
itself at once. 

If your boiler primes and water is carried over to the engine, 
it shows that there is want of sufficient steam room in the boiler.' 
Either put a dry-pipe in the boiler, or, increase the steam pressure 
if the boiler will safely stand it. 

Never attempt to calk a leaky seam in a boiler under steam 
pressure, because the jar caused by the hammer blows might 
cause a rupture of the seam. Better to be on the safe side 
Always when repairs are required in a steam boiler, and wait until 
the boiler is cold. The above applies to steam pipes and valve 
casings, also. 

| Never open any steam valves suddenly, nor close them sud- 
denly either, because it is highly dangerous to do so, particularly 
if there is considerable water in the pipes. The effect is the same 
as water hammer in water pipes. 
Smoke is caused by too little air supply, or by the flames being 



536 HANDBOOK ON ENGINEERING. 

prematurely cooled. Therefore, after firing up with fresh coal, 
it might be necessary to leave the furnace doors ajar in order to 
supply sufficient air above the fuel. 

Remember that it takes nearly 24 cubic feet of air for the 
proper combustion of one pound of soft coal. Hard coal does, 
not require so much. 

Each and every boiler in a battery should have its own inde- 
pendent safety-valve and steam gauge. 

If you are obliged to. force your fire, watch your furnace sheets 
for indications of " bagging," if the water space below the lowest 
row of tubes is cramped. Water-tube boilers are less liable to 
suffer from the effects of forced fires than shell boilers. 

With an intensely hot fire under a shell boiler, the furnace 
sheets are liable to bag, unless there is ample water space be- 
tween the shell of the boiler and the bottom row of tubes. 

The use of mineral oil to remove or prevent boiler scale, is not 
to be recommended. 

Have your feed water analyzed, and use a scale preventer 
adapted to its requirements. 

By all means endeavor to secure a steady furnace temperature, 
and a steady steam pressure, for herein lies much economy oi 
fuel. Fluctuations are wasteful. 

Put a damper in your chimney and adjust it to the needs oi 
your furnace. Try to prevail on your employer to put in a shak- 
ing grate. It will enable you to carry a steady furnace temper- 
ature, and also enable you to keep the air spaces in your grate 
free and open without breaking up your fire. 

RULES AND PROBLEMS RELATING TO STEAM BOILERS. 

To find the safe working pressure : — 

IL S. Rule, — Multiply one-sixth (|) of the lowest tensih 
strength found, stamped on any plate in the cylindrical shell 



HANDBOOK ON ENGINEERING. 537 

by the thickness — expressed in inches or parts of an inch — of 
the thinnest plate in the same cylindrical shell, and divide by the 
radius or half diameter — also expressed in inches — and the 
result will be the pressure allowable per square inch of surface 
for single riveting ; to which add 20 per cent for double riveting, 
when all the holes have been "fairly drilled" and no part of 
such hole has been punched. 

A. S. of M* E. Rule. — First, find the tensile strength of the 
solid plate between the centers of two adjacent rivet holes. Call 
this factor A. 

Next, find the tensile strength of the solid plate between the 
centers of two adjacent rivet holes, less the diameter of one rivet 
hole. Call this factor B. 

Next, find the shearing strength of the rivets. Call this 
factor C. 

Now divide whichever is the smaller factor B or G by A, and 
the quotient will give the strength of the joint as compared with 
the solid plate — expressed as a percentage. Then multiply the 
tensile strength of the plates by the thickness of plates — in frac- 
tional parts of an inch — and multiply this product by the per- 
centage as found above, and divide this last product by the 
radius of the shell in inches, and the quotient will be the bursting 
pressure. 

^ Divide this quotient by the factor of safety and the result will 
?ive the safe working pressure. 

Example, — What is the safe working pressure for a steel 
poller 60 inches in diameter, with side seams double riveted, 
Jensile strength^ of plates 60,000 lbs. per sqr. in., thickness of 
me I inch. Diameter of rivet holes if inch, pitch of rivets 3£ 
[nches, shearing strength of rivets 38,000 lbs. per sqr. in., and 
actor of safety 5 ? 

Ans. By U. S. rule, 150 lbs. per sqr. in. 
By A. S. of M. E. rule, 106| lbs. per. sqr. in. 



538 HANDBOOK ON ENGINEERING. 

Operation by U. S. rule: — 

60^000 _ i(} And ^ i()5000 x = 3750> 

6 

And, ^-=125. And, 125 X. 20 =25. 

Then, 125 +.25 = 15Q. 

Operation by A. S. of M. E. rule: — 
|" = .375". 

||" = .9375". 

Then, 60,000 X 3} X .375 == 73,125 lbs., the strength of the; 
solid plate between the centers of two adjacent rivet holes. Call 
this factor A. Also, 3J = 3.25. 

Then, 3.25 — .9375 = 2.3125. 

And, 60,000 X 2.3125 X .375 = 52,081.25 lbs. the strength: 
of the plate between two adjacent rivet holes. Call this factor B. 

Then, .9375 X -9375 X .7854 = .69029 of a square inch, the 
area of one rivet hole. There are two rows of rivets. 

Then, .69029 X 2 = 1.38058 sqr. ins. the area of two rivet 
holes combined. 

Then, 38,000 X 1.38058 = 52,462.04 lbs., the resistance oi 
rivets to shearing. Call this C. Now since B is less than C, 
divide 52,031.25 by 73,125 and get as a quotient .71 +, thus 
showing the strength orthe joint to be more than 71 per cent oi 
the strength of the solid plates. 

Then, gM 00 X ; 375 X - 71 =532.5 lbs. per sqr. in., ti§ 

bursting pressure. 

And, 532,5 = 106.5 lbs. per sqr. in., the safe working 
5 

pressure. 



HANDBOOK ON ENGINEERING. 539 

To find the horse power of a horizontal return tubular boiler, 
from its heating surface : — 

Rule* — Find the heating surface in square feet, of the shell 

of the boiler, measuring from one fire line to the other. Next 

j find the internal heating surface of all the tubes in square feet. 

Add the two results together and divide their sum by 12, and the 

| quotient will be the H. P. approximately. The heads are 

omitted. 

Example* — What is the H. P. of a horizontal return tubular 
boiler 60 inches iu diameter and 20 feet long, with 44 four-inch 
tubes each 20 feet long, the distance from fire line to fire line 
ibeing 9 feet? Ans. 86.65 H. P. 

Operation* — The internal diameter of a 4-inch tube is 3.732 
inches. 

Then, 20X9 = 180 square feet of heating surface in the 
shell. 

And, -^ *__: = .9770376 ft., the circumference of 

one tube in feet. 

And, .9770376 X 20 X 44 = 859.793 + sqr. ft., the total 
heating surface of the tubes. 

Then, H° + 8M-793 = 86 . 65 nearly . 

To find the factor of evaporation : — 

Rule* — From the total number of heat units in one pound of 
3team at the given pressure, subtract the number of heat units in 
one pound of the feed water at its given temperature, and divide 
the remainder by 965.7, which is a constant. 

Example* — A boiler evaporates 6,000 lbs. of water per hour 
from feed-water at 210 degrees into steam at 125 lbs. gauge pres- 



540 HANDBOOK ON ENGINEERING- 

sure, what is the equivalent evaporation "from and at," and 

what is the H. P. of the boiler? 

, Ans. Equiv. evap. 62/6 lbs. 
H. P. 182, nearly. 
Operation. — The total number of heat units in steam at 125 
lbs. per sqr. in. gauge pressue is 1221.5351. 

The number of heat units in feed-water at 210 degrees 
equals 210.874. The latent heat of steam at atmospheric pres- 
sure, equals 965.7. 

Then, 1221.5351—210.874 = 1010.6611. 

And 1Q 1Q - 6611 — 1.046, the factor of evaporation. 

' 965.7 
And, 6000 X 1-046 = 6276 the equivalent evaporation. 

Then, — = 181.9 H. P. 
34.5 

To find how many pounds of steam at a given absolute pressure 
will flow through an orifice of one square inch area in one sec- 
ond : — 

Rufe. Divide the absolute pressure by the constant number 70. 

Example. — How many pounds of steam at 85 lbs. per sqr. in. 
gauge pressure, will flow through an orifice one inch in diameter. 
mole second? Ans - 1422 1b* 

Operation. — A hole 1 inch in diameter has an area of .7854 
of a sqr. inch. 

And 85 + 15 =100 lbs. absolute. 

Then , ^x_!!^ =1 . 122 . 

The weight of a cubic foot of steam at 100 lbs. per sqr. in 

1 122 
absolute pressure is .2307 of a pound. Then, -^yj =N? 4.86 -+ 

cubic feet. 



HANDBOOK ON ENGINEERING. 541 

To find the width of a reinforcing ring for a round hole in a flat 
surface, when the ring must contain as many square inches as 
were cut out of the plate, and when the ring and the plate are of 
the same thickness : — 

Rule* — Find the area of the hole in square inches and multi- 
ply it by 2. Divide this product by .7854 and extract the square 
root of the quotient for the diameter of the ring over all. Sub- 
tract the diameter of the hole from the diameter over all, and 
divide the remainder by 2 for the width of the ring. 

Example* — What should be the width of a reinforcing ring for 
a hole 10 inches in diameter, the metal cut out, and the metal in 
the ring being § in. thick? Ans. 2 T ^- inches. 

Operation* — 10 X 10 X .7854 = 78.54 sqr. ins. area of hole. 

And, 78.54 X 2 — 157.08 sqr. ins. in both hole and ring. 
157.08 

And ' T785T = 20 °- 

And, sJ20d = U.U2+. 

And, 14.142 — 10 = 4.142. 

4.142 
Then, — ~ — = 2.071" or practically 2 x y. 

To find the width of a reinforcing ring for an elliptical manhole 
in a flat surface, when the ring must contain as many square 
inches as are contained in the hole, and the metal cut out and 
metal in the ring are of the same thickness : — 

Rule* — Square the short diameter of the hole and add to it six 
times the short diameter multipled by the long diameter, and to 
this product add the square of the long diameter, and extract the 
square root of the sum. From this root subtract the sum of the 
short diameter added to the long diameter, and divide the re- 
mainder by 4 for the width of the ring. 

Example. — What should be the width of a reinforcing ring 
for a manhole 11" X 15"? Ans. 2\\ inches. 



542 HANDBOOK ON ENGINEERING. 

Operation*— 11" X 11 ' = 121, 

And, 11 X 15 X6=990. 

And, 15 X 15 = 225. 

Then, 121 + 990 + 225 = 1336. 

And, V1336 = 36.551. 

And, 11 + 15 = 26. 

Then, 36.551 — 26 = 10.551. 

10.551 

And, — t — ~— 2.637 -j- ins. the width of the ring, or, prac- 
tically 2i£ ins. 

Then, 2.637 X 2=5.274". 

And, 11 + 5.274 = 16.274" short diameter of ring over all. 

And, 15 -f- 5.274 == 20.274" long diameter over all. 

Proof: 20.274 X 16.274 X .7854= 259.13 + square inches 
area of hole and ring. 

And, 15 X 11 X .7854 = 129.59 -\- sqr. ins. area of hole alone. 

Then, 259.13—129.59 = 129.54. 



THE AHOUNT OF STEAM USED WITH VALVE OPEN WIDE, 
WITH STEAH JETS AS A SMOKE PREVENTIVE. 

STEAM JETS. 

Given two boilers with separate furnaces, having 4 steam jets 
in each furnace, and each jet T ^- inch in diameter, the steam pres- 
sure being 100 lbs. per sqr. inch by the gauge. How many 
pounds of steam at this pressure will flow through the 8 nozzles 
in 12 hours? Answer. 1739 lbs. nearly. 

Operation : r \" = .0625 ". 

Then, .0625 X .0625 X .7854 = .003067968750 sqr. inch, 
area of 1 jet. 



HANDBOOK ON ENGINEERING. 543 

And, .003067968750 X^ = .02.454375 sqr. inch, the com- 
bined area of 8 jets. 

Also, 100 + 15 = 115 lbs. per sqr. inch, the absolute steam 
pressure* . 

115 

And, === 1.64 lbs. of steam per second that will flow 

70 1 

through an orifice of 1 square inch area. 

Then, 1.64 X .02454375 = .04025175 lbs. of steam per second 

flowing through the 8 jets. 

Again: There are 43,200 seconds in 12 hours. 

Thus : 12 X 60 X 60 = 43,200. 

Then, .04025175 X 43,200 = 1738.8756 lbs. of steam will 

flow through 8 jets in 12 hours' time. 

Taking a high speed automatic cut-off engine using 20 lbs. of 

steam per H. P. per hour, the 8 steam jets would waste enough 

steam in 12 hours to run — 

A 10 H. P. engine for 8 J hours. 

A 20 " " " 4£ " 

A 40 " " " 2| 6 

An 80 " " " 1 T ^ « 

Thus^lO X 20 = 200. 

And, = 81 nearly. 

'200 * J 

20 X 20 = 400. 

And, = 4i nearly. 

400 4 J 

80 X 20 == 1600. 

A , 1739 1 t . 

And, = 1 T V nearly. 

1600 T¥ J 



544 



HANDBOOK ON ENGINEERING, 



THE STEAM PUMP. 



CHAPTER XIX 




The Worthington Compound Pump. 



THE WORTHINGTON COMPOUND PUMP. 

In the arrangement of steam cylinders here employed, the steam 
is used expansively, which cannot be done in the ordinary form. 
Having exerted its force through one stroke upon the smaller 
steam piston, it expands upon the larger during the return stroke, 
and operates to drive the piston in the other direction. This is, 
in effect, the same thing as using a cut-off on a crank engine, 
only with the great advantage of uniform and steady action upon 
the water. 



HANDBOOK ON ENGINEERING. 



545 



Compound cylinders are recommended in any service where 
the saving of fuel is an important consideration, hi such cases. 
their greater first cost is fnlly justified, as they require 30 to 33 
per cent less coal than any high-pressure form on the same work. 



r*\ 




The above illustration 
Compound Pump - 



s a sectional view of the Worthington 
- This cut shows the steam valves 
properly set. 



On the larger sizes, a condensing apparatus is often added, thus 
securing the highest economical results. 

Any of the ordinary forms of steam pumps can be fitted with 
compound cylinders. 

It should be remembered that, as the compounds use less steam 
their boilers may be reduced materially in size and cost, compared 
with those required by the high-pressure form. This principle of 
expansion without condensation cannot be used with advantage 
Where the steam pressure is below 75 lbs. 

35 



546 



HANDBOOK ON ENOINKF/K I NO . 



*J 









The Deane Pump. 




The above is a sectional view of the 

DEANE DIRECT ACTING STEAM PUMP. 

The operation of the steam valves* — In the Deane Steam 
Pump a rotary motion is not developed by means of which an 



HANDBOOK ON ENGINEERING. 



547 



eccentric can be made to operate the valve. It is, therefore, 
necessary to reverse the piston by an impulse derived from itself 
at the end of each stroke. This cannot be effected in an ordinary 
single-valve engine, as the valve would be moved only to the cen- 
ter of its motion, and then the whole machine would stop. To 
overcome this difficulty, a small steam piston is provided to move 
the main valve of the engine. In the Deane Steam Pump, the 
lever 00, which is carried by the piston rod, comes in contact 




This cut shows the valves properly set. 



with the tappet when near the end of its motion, and by means 
of the valve-rod 24, moves the small slide-valve which operates 
the supplemental piston 9. The supplemental piston, carrying 
with it the main valve, is thus driven over by steam and the 
engine reversed. If, however, the supplemental piston fails 
accidentally to be moved, or to be moved with sufficient prompt- 
ness by steam, the lug on the valve-rod engages with it and 
compels its motion by power derived from the main engine. 



548 



HANDBOOK ON ENGINEERING. 




SECTIONAL VIEW OF 



'The Cameron" >5team Pump 



The above is a sectional view of the steam end of a Cameron 
pump. 

Explanation s A is the steam cylinder ; 0, the piston ; Z>, the 
piston rod ; A, the steam chest; F, the chest piston or plunger, 
the right-hand end of which is shown in section ; G, the slide 
valve ; _H", a starting bar connected with a handle on the outside ; 
// are reversing valves ; A 7 " A" are the bonnets over reversing valve 
chambers ; and E E are exhaust ports leading from the ends of | 
steam chest direct to the main exhaust, and closed by the revers- 
ing valve II; Nis the body piece connecting the steam and water 
cylinder,, 



HANDBOOK ON ENGINEERING. 549 

Operation of the Cameron Pump : Steam is admitted to the 
steam chest, and through small holes in the ends of the plunger ; 
F fills the spaces at the ends and the ports E E as far as the 
reversing valves II; with the plunger F and slide valve G in 
position to the right (as shown in cut), steam would be admitted 
[to the right-hand end of the steam cylinder A, and the piston C 
would be moved to the left. When it reaches the reversing valve 
/ it opens it and exhausts the space at the left-hand end of the 
plunger F, through the passage E; the expansion of steam at the 
right-hand end changes the position of the plunger F, and with it 
the slide valve (7, and the motion of the piston C is instantly 
reversed. The operation repeated makes the motion continuous. 
In its movements, the plunger F acts as a slide valve to shut off 
the ports E E, and is cushioned on the confined steam between 
the ports and steam chest cover. The reversing valves I I are 
closed immediately the piston C leaves them , by pressure of steam 
on their outer ends, conveyed direct from the steam chest. 

Operation* — Supposing the steam piston C moving from right 
to left: When it reaches the reversing valve I it opens it and 
exhausts the space on the left-hand end of the plunger F, through 
the passage E, which leads to the exhaust pipe ; the greater pres- 
sure inside of the steam chest changes the position of the plunger 
Fand slide valve G, and the motion of the piston C is instantly 
reversed. The same operation repeated at each stroke makes the 
motion continuous. The reversing valves II are closed by a pres- 
sure of steam on their large ends, conveyed by an unseen passage 
direct from the steam chest. When a pump is first connected, 
remove the bonnets K K and valves 1 1 and blow steam through 
to remove any dirt, oil or gum that may be lodged in the steam 
ports. Take valve F, valve G and II out and wipe off with 
clean waste, and then oil and put back. Then see that the pack- 
ing is not too tight. When a Cameron pump has been run along 
time, the plunger F becomes worn and leaks enough steam to 



550 



HANDBOOK ON ENGINEERING. 



cause the valve F to become balanced. The effect of this is, the 
pump will remain on the end ; to overcome this, take out plunger 
F, or piston, as it is called by some, and drill the little hole that 
you will find in the ends of same a little larger, say about one- 
fourth larger ; that will increase the pressure on both ends oi 
plunger F; as soon as the piston comes in contact with valve J 
the steam is exhausted to exhaust pipe. 




The above is a sectional cut of 



THE KNOWLES DIRECT AGTING STEAH PUMP. 



Explanation of steam valves, etc* — The Knovvles, in fact, a| 
first-class direct acting steam pumps, is absolutely free from what 
is termed a " dead center," when in first-class order. 

This feature in the Knovvles Pump is secured by a very simple 
and ingenious mechanical arrangement, i. p., by the use of an) 
auxiliary piston which works in the steam chest and drives the 
main valve. This auxiliary or ww chest piston," as it is called, is 
driven backward and forward by the pressure of steam, carrying 



HANDBOOK ON ENGINEERING. 



551 



with it the main valve, which valve, in turn, gives steam to the 
main steam piston that operates the pump. This main valve is a 
plain slide valve of the B form, working on a flat seat. The chest 
piston is slightly rotated by the valve motion ; this rotative move- 
ment places the small steam ports, D, E, F (which are located in 




The Knowles Direct Acting Steam Pump. 

the under side of the said chest piston) , in proper contact with 
corresponding ports A B cut in the steam chest No. 31. The 
steam entering through the port at one end and filling the space 
[between the chest piston and the head, drives the said piston to 
fthe end of its stroke and, as before mentioned, carries the main 
slide valve with it. When the chest piston has traveled a certain 
distance, a port on the opposite end is uncovered and steam there 
enters, stopping its further travel by giving it the necessary 



552 



HANDBOOK ON ENGINEERING. 



cushion. In other words, when the rotation motion is given to j 
the auxiliary or valve driving piston by the mechanism outside, 
it opens the port to steam admission on one end, and at the same 
time opens the port on the other end to the exhaust. 




This cut shows the valves properly set. 



Operation of the Knowles Pump is as follows : The piston rod, 
with the tappet arm, moves backward and forward from the 
impulse given by the steam piston. At the lower part of this 
tappet arm is attached a stud or bolt, on which there is a friction 
roller. This roller coming in contact with the " rocker bar" at 
the end of each stroke, operates the latter. The motion given the 
c ' rocker bar ' ' is transmitted to the valve rod by means of the 
connection between, causing the valve rod to partially rotate. 
This action, as mentioned above, operates the chest piston, which 
carries with it the main slide valve, the said valve giving steam to 
the main piston. The operation of the pump is complete and 



HANDBOOK ON ENGINEERING. 553 

continuous. The upper end of the tappet arm does not come in 
contact with the tappets on the valve rod, unless the steam pres- 
sure from any cause, should fail to move the chest piston, in which 
case the tappet arm moves it mechanically. 

NOTICE. 

1. Should the pump run longer stroke one way than the other, 
simply lengthen or shorten the rocker connection (part 25) so 
that rocker bar (part 23) will touch rocker roller (20) equally 
distant from center (22). 

2. Should a pump hesitate in making its return stroke, it is be- 
cause rocker roller (20) is too low and does not come in contact 
with the rocker bar (23) soon enough. To raise it, take out 
rocker roller stud (20 A), give the set screw in this stud a suffi- 
cient downward turn, and the stud with its roller may at once be 
raised to proper height. 

3. Should valve rod (17) ever have a tendency to tremble, 
slightly tighten up the valve rod stuffing box nut (28) . When 
the valve motion is properly adjusted, tappet tip (16) should 
not quite touch collar (15) and clamp (27). Rocker roller 
(20), coming in contact with rocker bar (23) will reverse the 
stroke. 

Operation and construction of the 

HOOKER DIRECT=ACTING STEAM=PUMP. 

The parts being in position, as shown, the steam on being ad- 
mitted to the center of the valve chamber, brings its pressure to 
bear on the main and supplemental flat slide valve 4 and 7, and 
also within the recess in the center of the supplemental piston 6. 
The recess incloses the main valve 4, so that this valve will move 
with the supplemental piston whenever the steam is supplied to 



554 



HANDBOOK ON ENGINEERING. 



and exhausted from each end of this piston. The live steam 1 
passes through the left-hand ports A 1 B 1 , driving the main piston 
2 to the right, and the exhaust passes out through the right-hand 
ports ^1 and C under the cavity in the main valve 4 to the atmos- 
phere. As the main piston nears the right hand port, the valve 
lever 13, which is attached to the piston rod 3, brings the dog 1 7, 
in plate 16, in contact with the valve arm 15, and moves the sup- 
plemental valve 7 to the right, thus supplying live steam to the 




right of the supplemental piston 6, and exhausting from the left 
through the ports e e. As the supplemental piston incloses the 
main valve, this valve is carried with it to the left. Steam now 
enters the right-hand ports ^1 B and is exhausted from the left- 
hand main port . 1 . The engine commences its return stroke and 
the operation just described becomes continuous. As the main 
piston (2) closes the main port (^i) to the right, it is arrested on 
compressed exhaust steam. The main valve 4 having closed the 
auxiliary ports (B) leading to that end of the main cylinder, the 



HA^DliOOK ON ENGINEERING. 



555 




This cut shows the steam valves properly set. 



steam being supplied through both the main and auxiliary ports, 
but released through the main ports only. 



BLAKE STEAM PUHP. 

Description of the Blake Steam Pump. - The Blake Steam 
Pump is absolutely positive in its action ; that is to say, the 
operation at the slowest speed under any pressure, is perfectly 
continuous, and the pump is never liable to stop as the main valve 
passes its center, if the pump is in good order. An ingenious and 
simple arrangement is used in the Blake Pump to overcome the 
| dead center," as will be seen from the engravings. 

Operation of the Blake Steam Pump- — The main or pump 
driving piston .1 could not be made to work slowly were the 
main valve to derive its movement solely from this piston ; for 



556 HANDBOOK ON ENGINEERING. 

when this valve had reached the center of its stroke, in which 
position the ports leading- to the main cylinder would be closed, 




The Blake Steam Pump. 

no steam could enter the cylinder to act on said piston, con- 
sequently, the latter would come to rest, since its momentum 
would be insufficient to keep it in motion, and the main 
valve would remain in its central position or Li dead cen- 
ter." To shift this valve from its central position and 
admit steam in front of the main piston (whereby the motion 
of the piston is reversed and its action continued), some agent 
independent of the main piston must be used. In the Blake 
Pump, this independent agent is the supplemental or valve-driving 
piston B. The main valve, which controls the admission of steam 
to, and the escape of steam from, the main cylinder, is divided 
into two parts, one of which, C, slides upon a seat on the main 
cylinder, and, at the same time, affords a seat for the other para 



HANDBOOK ON ENGINEERING. 



557 



D, which slides upon the upper face of C. As shown in the en- 
graving, D is at the left-hand end of its stroke, and C at the 
opposite, or right-hand end of its stroke. Steam from the steam- 
chest J is, therefore, entering the right-hand end of the main 
cylinder through the ports E and H, and the exhaust is escap- 
ing through the ports H 1 and E 1 , K and Jf, which causes the 




Sectional views of steam cylinder, valves, etc. 
of the Blake Steam Pump. 



main piston A to move from right to left. When this piston has 
nearly reached the left-hand end of its cylinder the valve motion 



558 



HANDBOOK ON ENGINEERING. 



(not shown) moves the valve-rod P, and this causes G Y , together 
with its supplemental valve B and S S 1 (which form, with (7, one 
casting) to be moved from right to left. This movement causes 
steam to be admitted to the left-hand end of the supplemental 
cylinder, whereby its piston B will be forced toward the right, 
carrying D with it to the opposite or right-hand end of its stroke ; 
for the movement of S closes N (the steam port leading to the 




This cut shows the valves properly set. 



right-hand end), and the movement of S 1 opens N 1 (the port 
leading to the opposite, or left-hand end). At the same time the 
movement of O opens the right-hand end of the cylinder to 
the exhaust through the exhaust ports X and Z. The ports C 
and D now have positions opposite to those shown in the engrav- 
ings, and steam is, therefore, entering the main cylinder through 
the ports E 1 and H 1 , and escaping through the ports //, E, K 
and il/, which will cause the main piston A to move in the op- 



HANDBOOK ON ENGINEERING. 559 

posite direction, or from left to right, and operations similar to 
those already described will follow, when the piston approaches 
the right-hand end of its cylinder. By this simple arrangement 
the pump is rendered positive in its action ; that is, it will in- 
stantly start and continue working the moment steam is admitted 
to the steam chest. The main piston A cannot strike the head of 
the cylinder, for the main valve has a head ; or, in other words, 
steam is always admitted in front of said piston just before it 
reaches either end of its cylinder, even should the supplemental 
piston B be tardy in its action and remain with D at that end, 
toward which the piston A is moving ; for C would be moved far 
enough to open the steam port leading to the main cylinder, since 
the possible travel of C is greater than that of D. The supple- 
mental piston B cannot strike the heads of its cylinders, for in its 
alternate passage beyond the exhaust ports X and X, it cushions 
on the vapor intrapped in the ends of this cylinder. 

MISCELLANEOUS PUfiP QUESTIONS. 

Q. What is a pump? A. It is hard to get a definition that 
will cover the whole ground. A pump may be said to be a 
mechanical contrivance for raising or transferring fluids ; and as a 
general thing consists of a moving piece working in a cylinder or 
other cavity ; the device having valves for admitting or retaining 
the fluids. 

Q. What two classes of operations are included in the term 
" raising " fluids? A. They may be raised by drafting or suc- 
tion, from their level to that of the pump ; they may be raised 
from the level of the pump to a higher level. 

Q. Do pumps always "raise" by either method, from one 
level to a higher one, the liquid which they transfer? A. No ; in 
many cases the liquid flows by gravity to the pump ; and in some 
it is delivered at a lower level than that at which it is received. 



560 HANDBOOK ON ENGINEERING. 

Q. Where a pump is not used for raising a liquid to a higher 
level, for what is it generally used ? A. To increase or decrease 
its pressure. 

Q. What classes of liquids are handled by purups ? A. Air, 
ammonia, lighting gas, oxygen, etc. 

Q. Name some liquids which are handled by pumps? A. 
Water, brine, beer, tan liquor, molasses, acids and oils. 

Q. Where it is not specified whether a pump is for gas or for 
liquid, which is generally understood? A. Liquid. 

Q. What gas is most frequently pumped? A. Air. 

Q. What liquid is generally understood if none other is speci- 
fied for a pump? A. Water. 

Q. Can pumps handle hot and cold liquids? A. Yes ; though 
cold are easier handled than hot. 

Q. What is the difference between a fluid and a liquid? A. 
Every liquid is a fluid ; every fluid is not a liquid. Air is a fluid ; 
water is both a fluid and a liquid. Every liquid can be poured 
from one vessel to another. 

SUCTION. 

Q. What causes the water to rise in a pump by so-called 
suction? A. The unbalanced pressure of the air upon the surface 
of the liquid below the pump, forces the water up into the suction 
pipe when the piston is withdrawn from the liquid. 

Q. How much is the pressure of the atmosphere? A. At the 
sea level about 14.7 lbs. per square inch, or 2116.8 lbs. per square 
foot. 

Q. In what direction is this pressure exerted? A. In eveiy 
direction equally. 

Q. What tends to prevent the water from being lifted? A. 
The force of gravity, which is the result of the attraction of the 
earth's center. 



HANDBOOK ON ENGINEERING. 561 

Q. In what direction does the force of gravity act? A. In 
radial lines towards the center of the earth. 

Q. With what force does this gravity act? A. That depends 
upon the substance upon which it is acting. 

Q. Why do you refer to the level of the sea in speaking of the 
pressure of the air and the weight of water? A. Because the air 
pressure becomes less as, in rising above the sea level, we recede 
from the center of the earth, and the weight of a given quantity 
of water or any other substance becomes less than it is at the level 
of the sea, as we approach to or recede from the center of the 
earth. 

Q. How is it that the weight of any substance becomes less if 
you go either above or below the sea level? A. The farther you 
go from the earth, the less its attraction and the less a given 
body will weigh upon a spring balance. The farther down into 
the earth you go, the nearer you get to the center of the earth, at 
which, there being attraction upon all sides, any body would 
weigh nothing. Going from the surface of the earth towards its 
center, then, a body weighs less and less upon a spring balance. 

Q. Why do you specify a spring balance?' A. Because in 
weighing by counterpoise, both the body to be weighed and the 
counterpoise by which it is weighed, would change their weights 
in the same proportion, as the position with regard to the center 
of the earth was changed. 

Q. What are the causes which principally prevent pumps from 
lifting up to the normal maximum? A. Friction ; leakage of air 
into the suction, chokes in the suction pipe. 

Q. Can a liquid be "drafted" without the expenditure of 
work ? A. No ; in drafting a liquid to the full height to which it 
can be drafted, at least as much power must be expended as 
would lift the same weight of liquid that height by any mechan- 
ical means ; only the amounts of friction being different. 

Q. Then what advantage is there in having a punip draft its 
36 



562 HANDBOOK ON ENGINEEPvING. 

water to the full possible height, over having it force tht water 
the full height? A. Convenience in having the pump higiier up. 

Q. Can a pump throw water higher or farther, with a given 
expenditure of power, where it flows in, than where it mast draft 
its water? A. Yes; on the same principle that it can throw 
farther or force harder when the water is forced to its suction 
side than where it merely flows in. 

Q. What is the use of the suction chamber? A. To enable 
the pump barrel to fill where the speed is high ; to prevent 
pounding, when the pump reverses. 

Q. Upon what does the lifting capacity of a pump depend? 
A. When the pump is in good order its lifting capacity depends 
mainly upon the proportion of clearance in the cylinder and valve 
chamber to the displacement of the piston and plunger. 

Q. Which will lift further, an ordinary piston pattern pump or 
a plunger pump ? And why? A. Other things being as nearly 
equal as they can be made between these two pumps, the piston 
pump will lift the farther of the two, because the plunger pump 
has the most clearance. 

Q. What is the advantage of the suction chamber? A. To 
assist the pump in drafting, especially at high speed. 

Q. What is the advantage of the air chamber? A. To make 
the stream steady. 

,Q. What difficulty is sometimes met with in using an air 
chamber? A. Where the pressure is very great sometimes the 
air is absorbed by the water, and thus the cushion is detroyed. 

FORCING. 

Q. What will be the volume of the air in the air chamber of a 
force pump, when the pump is forcing against a head of 67. G 
feet? A. It will be reduced to half its ordinary volume, because 
it will be at the pressure of two atmospheres. 



HANDBOOK ON ENGINEERING. 



563 




The above cut shows a pump with a removable cylinder 
or liner, and is packed with fibrous packing set out by adjustable 
set screws and nuts. This style of a pump is the best for small 
water-works or elevators, or where a pump is used where the 
water is muddy or sandy. 

To find the horse power necessary to elevate water to a 
given height : Multiply the total weight of the water in pounds 
by the height in feet and divide the product b} 7 33,000 (an allow- 
ance of 25 per cent should be added for water friction, and a further 
allowance of 25 per cent for loss in steam cylinder.) 

The heights to which pumps will force water when running at 



564 HANDBOOK ON ENGINEERING. 

100 feet piston speed per minute, and the suction and discharge 
pipes being of moderate length, will be found by dividing the area 
of the steam piston by the area of the water piston, and multi- 
plying the quotient by the steam pressure. Deduct 40 per cent 
for friction and divide the remainder by .434. 

Example* — To what height will an 8-inch steam piston, with 
a 5-inch water piston, force water, the steam pressure being 80 
lbs. by gauge? Ans. 283 ft. nearly. 

Operation* — Area of steam piston = 50.26 sq» ins. 
" " water " =19.63 " " 

Then, 4^ = 2.56. And 2.56 X 80 = 204.80 lbs. 
19.6b 

Then, 204.80 less 40% = 122.88 lbs. 

122.88 
And, — — - == 283 -f feet. 
.434 

An allowance must be made where long pipes are used. 

The normal speed of pumps is taken at 100 piston feet per 
minute, which speed can be considerably increased if desired. 

For feeding boilers, a speed of 25 to 50 piston feet per minute 
is most desirable. 

A gallon of water, U. S. Standard, weighs 8^ lbs. and contains 
231 cubic inches. 

A cubic foot of water weighs 62.425 lbs. and contains 1,728 
cubic inches, or 7 \ gallons. 

Doubling the diameter of a pipe increases its capacity four 
times. 

Friction of liquids in pipes increases as the square of the 
velocity. 

'To find the area of a piston, square the diameter and multiply 
by .7854. 



HANDBOOK ON ENGINEERING. 565 

Boilers require, for each nominal horse-power, about one cubic 
foot of feed water per hour. 

In calculating horse power of tubular or flue boilers, consider 
15 square feet of heating surface equivalent to one nominal horse- 
power. 

To find the pressure in pounds per square inch of a column 
of water, multiply the height of a column in feet by .434. 
Approximately, we say that every foot of elevation is equal to 
one-half lb. pressure per square inch; this allows for ordinary 
friction. 

The area of the steam piston, multiplied by the steam pressure, 
gives the total amount of pressure that can be exerted. The 
area of the water piston, multiplied by the pressure of water per 
square inch, gives the resistance. A margin must be made 
between the power and the resistance to move the pistons at the 
required speed— say from 20 to 40 per cent, according to speed 
and other conditions. 

To find the capacity of a cylinder in gallons : Multiplying the 
area in inches by the length of stroke in inches will give the total 
number of cubic inches ; divide this amount by 231 (which is the 
cubical contents of a gallon of water) and quotient is the capacity 
in gallons. 

To find quantity of water elevated in one minute running at 100 
feet of piston speed per minute: Square the diameter of water 
. cylinder in inches and multiply by 4. 

Example: Capacity of a five-inch cylinder is desired. The 
square of the diameter (5 inches) is 25, which, multiplied by 4, 
gives 100, which is gallons per minute, approximately. 

Q. " What is the reason that a steam pump of the horizontal 
double acting type should throw an intermitting stream under 
pressure, like the stream from milking a cow, only not quite so 
bad as that? I have tried valves of different sizes, with different 
amount of rise, springs or valves of different tension, different 



566 HANDBOOK ON ENGINEERING. 

kinds of packing in water piston, and different sized water port? 
or passages, without any apparent difference." A. Steam pumps 
of the horizontal double-acting type are not alone in throwing an 
intermitting stream. The same thing shows up in vertical single- 
acting pumps ; and all horizontal double-acting pumps do not so 
behave. The steam fire engine shows that no type of pump is 
exempt from tc squirting." 

Q. How may this squirting be lessened? A. By increasing 
the suction valve area ; by giving more suction chamber and 

more air chamber. 

******** 
Q. What is a sinking pump? A. One which can be raised and 
lowered conveniently, for pumping out drowned mines, etc 

Q. Into what main general classes may reciprocating cylinder 
pumps be divided? A. Into single acting and double acting. 

Q. What is a single acting reciprocating pump ? A. One in 
which each reciprocation or single stroke in one direction causes 
one influx of fluid, and each reciprocation or single stroke in the 
opposite direction causes one discharge of fluid. In other words, 
the pump, as regards its action, is single ended. 

Q. What is a double acting reciprocating pump? A. One in 
which each end acts alternately for suction and discharge. -Re- 
ciprocation of the piston in one direction causes an influx of 
fluid into one end of the pump from the source, and a discharge 
of fluid at the opposite end ; on the return stroke the former 
suction end becomes the discharge end. In other words, the 
pump is double ended in its action ; or is " double-acting." 

Q What is the special advantage of having double-acting 
pump cylinders? A. The column of water is kept in motion 
more constantly, and hence there is less jar ; smaller pipes may 

be used. 

******** * * * * 

Q. How may those pumps which are driven by steam against a 



HANDBOOK ON ENGINEERING. 567 

steam piston be divided? A. Into those which have a fly wheel 
and those which have no fly wheel. 

Q. Into what classes may those pumps which are driven by 
steam, without a flywheel, be divided? A. Into direct acting 
and duplex. 

Q. What is the advantage of a fly wheel steam pump? A. 
Steadiness of action ; the capability of using the steam expan- 
sively. 

Q. What are the disadvantages of fly wheel pumps? A. Great 
weight ; inability to run them very slowly without gearing down 
from the fly wheel shaft, as the wheel must run comparatively 
rapidly. 

Q. What is a direct-acting steam pump? A. One in which 
there is no rotary motion, the piston being reversed by an impulse 
derived from itself at or near the end of each stroke. There is 
but one steam cylinder for one water cylinder ; the valve motion 
of the steam cylinder being controlled by the action of the steam 
in that cylinder. 

HOW TO SET THE STEAM VALVES ON A DUPLEX PUMP. 

The steam valves on Duplex pumps generally have no outside 
lap, consequently, when in its central position, it just covers the 
steam ports leading to the opposite ends of cylinder. 

By lost motion is meant, the distance a valve-rod travels 
before moving the valve; if the steam-chest cover is off the 
amount of lost motion is shown by the distance the valve can be . 
moved back and forth before coming in contact with the valve- 
rod nut. The object of lost motion is to allow one pump to 
almost complete its stroke before moving the valve of its fellow 
engine. As the steam piston is nearing the end of its stroke, it 
moves the valve of its fellow engine, admitting steam and start- 
ing its fellow engine as it lays down its own work ; in other words, 



568 



HANDBOOK ON ENGINEERING. 



the other picks it up. The amount of lost motion required is 
enough to allow each piston to complete its stroke; in other words, 
if there was no lost motion, as each piston would pass the 
center of their travel, they would move the valve of their 
fellow engine, and the result would be a very short stroke. 




This cut shows the steam valves properly set. 



To set the steam valves, move the steam piston towards the 
steam cylinder head until it comes in contact with the head ; mark 
with a scribe on the piston-rod at the face of the stuffing-box 
follower on steam end ; then move the piston to its contact stroke 
on the opposite end and make another mark on the piston-rod, 
exactly half way between the face of the stuffing-box follower on 
the steam end, and the first mark. Then move the piston back 
until the middle mark is at the face of piston-rod stuffing-box 
follower on the pump end. This operation brings the piston 
exactly in the middle of the stroke. Then takeoff the steam 



HANDBOOK ON ENGINEERING. 569 

chest cover, place the slide-valve in the center, exactly over the 
steam ports. Place the slide-valve nut in exact center between 
the jaws of the slide-valve, screw the valve-rod through the nut 
until the eye on the valve-rod head comes in line with the eye of 
the valve-rod link ; slip the valve-rod head pin through head and 
the valve is set. Repeat the same operation on the other side of 
the pump. Where a pump is fitted with four hexagon valve-rod 
nuts, two either end of the slide-valve, instead of one nut in the 
center of the valve, set and lock these hexagon nuts at equal dis- 
tances from the outer end of the slide-valve jaws, allowing a little 
lost motion, varying from J" on high-pressure pumps, to, say, 
J" on low service pumps, on each side of valve ; if the steam 
piston hits the head, take up some of your lost motion ; if the 
steam piston should not make a full stroke, give more lost motion. 

THE BEST MANNER OF ARRANGING PIPE CONNECTIONS. 

For the purpose of showing good arrangement, the following 
cut is presented. 

On long- lifts it is necessary to provide the suction pipe S 
with a foot-valve F. By the use of a foot-valve, the pipe and 
cylinders are constantly kept charged with water, allowing the 
pump to start without having to free itself and the suction pipe 
of air. In case of a long lift, the vacuum chamber V is also 
essential. This may be readily constructed by using a tee in place 
of the elbow 2£, extending the suction pipe and placing a cap 
upon the top. In order to keep the water back when the pump is 
being examined or repaired, a gate valve should be placed in the 
delivery pipe. It sometimes happens that, either purposely or 
through a leak in the foot-valve, the suction chamber becomes 
empty. For the purpose of charging the suction pipe and cylin- 
der a " charging pipe " P is placed outside the check valve, 
connecting the delivery pipe D with the suction. In order that 



570 



HANDBOOK ON ENGINEERING. 



the pump, in starting, may free itself of air, a check valve C- and 
a " starting pipe " A should be provided. This pipe may be 




ARRANGEMENT OF PIPE CONNECTIONS. 



led to any convenient place of discharge. After the pump has 
started, the valve in the starting pipe should be closed gradually. 
Faulty connections are generally the cause of the improper action 



HANDBOOK ON ENGINEERING. 571 

of a pump. Great care should, therefore, be taken to have 
everything right before starting. A very small leak in the suc- 
tion will cause a pump to work badly. 

Q. What is the peculiarity of the duplex type? A. There are 
two steam cylinders and two water cylinders ; the piston of one of 
these cylinders works the valve of the other cylinder, and vice versa. 
Neither half can work alone. This name is entirely arbitrary. 

Q. How would you call a pumping machine in which there are 
two steam cylinders, each operating a water cylinder in line with 
it ; each half being a perfect pumping machine independent of the 
other side? A. A " double " pump. 

Q. Can a direct acting steam pump use steam expansively ? 
A. Not to any extent ; in fact, there would be danger of sticking 
upon the centers in most cases, if there was lap and expansion. 

Q. What is the reason that a single cylinder engine cannot well 
reverse itself without a fly wheel, by means of the ordinary single 
D valve? A. Because when the valve was at mid-travel, both 
ports of the valve seat would be closed by the valva faces, and 
neither exhaust nor admission take place. 

Q. What means are employed in a direct acting steam pump to 
move the valve? A. A small supplementary piston is used; this 
supplementary piston being actuated by the main piston in any 
one of several different ways. 

Q. What are the principal ways of working the supplementary 
piston from the main piston? A. (1) The main piston strikes 
the tappet of a small valve, which opens an exhaust passage in 
one end of the cylinder, containing a supplementary piston, and 
having live steam pressing upon both ends of the supplementary 
piston ; (2) by the main piston striking a rod passing through 
the cylinder head, and moving a lever which controls the motion 
of the part of the main valve to which is attached the valves which 
moves the supplementary piston ; (3) the main piston rod carries 
a tappet arm, which twists the stem of the supplementary piston t 



572 HANDBOOK ON ENGINEERING. 

thus uncovering ports which cause its motion ; (4) a projection 
upon the main piston rod engages the stem and operates the valve 
which moves the supplementary piston, but if that valve should 
not, by means of its steam passages, cause quick enough or sure 
enough motion of the supplementary piston, a lug upon this stem 
moves the supplementary piston. 

Q. In the first of these four classes, what is the principal 
element in the valve motion ? A. A difference in area between 
the eduction port of the supplemental piston and its induction port 

Q. What is the principal feature in the second class? A. A 
regular slide valve letting steam upon alternate ends of the sup- 
plemental piston. 

Q. In the third class, what is the main feature? A. A twist- 
ing motion in the supplemental piston. 

Q. In the fourth class, what is the principal feature? A. 
Movement of the supplemental piston by steam controlled by a 
slide valve, and by the mechanical action of the slide valve itself 
if its steam distribution is defective. 

Q. What are the objections to most pumps of the direct acting 
type? A. The unbalanced condition of the auxiliary pistons in 
the exhaust side, causing a loss of steam when the parts are worn, 
the choking up of the small ports for the auxiliary pistons, by the 
gumming and caking of the oil therein. 

Q. Can the ordinary direct acting steam pump use steam 
expansively? A. No. 

Q. How may this be done? A. By compounding. 

Q. What is to be taken into consideration in the use of com- 
pound steam pumps? A. That they are designed for a certain 
range of pressure — say from 80 to 120 pounds boiler pressure, 
and will do their best work between these pressures. 

Q. Have all direct-acting steam pumps intermittent valve 
motion? A. No; there are some which have continuous valve 
motion. 



HANDBOOK ON ENGINEERING. 573 

Q. In most direct-acting steam pumps, are the auxiliary piston 
heads made together or in separate pieces? A. Together. 

Q. They are in contact with the steam in the chest? A. Yes. 

Q. What should be said about the location of a pump? A. It 
should be as "near the source of supply as is convenient. 

Q. What may be said about convenience in repairs? A. The 
pump should have room left upon all sides ; and upon both ends 
equal to its length, for the removal of the piston rods in case of 
j repairs. 

Q. If the floor is not strong enough, how may a good founda- 
tion be made? A. By digging two or three feet into the ground 
and building up the proper height with stone or brick laid in 
strong cement, with a cap stone. 

Q. What may be said about suction pipes? A. They must be 

as large as possible ; the longer they are the greater in diameter 

! they should be ; they should be as straight as possible, and as 

free from bends and valves ; they must be air-tight ; they must 

not be allowed to get obstructed by foreign substances. 

Q. What may be said about the area of strainer holes? A. 
They should have an aggregate area about five times that of the 
suction pipe. 

Q. Where are foot valves necessary ? A. Upon long suctions 
or high lifts. 

Q. Should two pumps take their suction from one pipe ? A. It 
should be avoided, unless the pipe is very large ; and in case both 
suctions should be arranged so that one of the pumps should not 
have to draft at right-angles to the flow of water going to the other 
pump. 

Q. What arrangement should be made where it is necessary to 
have two pumps draft from one suction? A. There should be a 
Y connection. 

Q. What is a good way to reduce the friction in suction pipes 
where there are many bends? A. To use bends of wrought- 



574 HANDBOOK ON ENGINEERING. 

iron pipe of as long a radius as possible, instead of cast-iron 
elbows. 

Q. What may be said about the lower end of the suction pipe? 
A. It should generally have a strainer ; and if the lift is over 12 
to 15 feet, should have a foot valve. 

Q. What is a good thing to do with the discharge pipe near 
the pump? A. To put a valve in it near the pump, to keep 
the water in the pipe when the water end is to be opened for 
inspection or repairs., 

Q. What provision should be made for priming the pump? A. 
There should be a pipe with a stop valve in it connected from the 
discharge pipe beyond this check valve, or from some other source 
of supply, to the suction pipe, for the purpose of priming the 
pump. 

Q. When the pump is in position for piping, what care should 
be taken? A. That the pipes are of proper length, so as not to 
bring any undue strain upon them in connecting them to the pump 
as in that case they will be liable to give trouble by breaking or 
working the joints loose and leaking. 

Q. Does any pipe have an effective diameter as great as its 
nominal diameter? A. No; because the sides retard the flow of 
the liquid ; there is a neutral film of liquid which practically does 
not move. 

Q. Upon what does the thickness of this lilmof liquid depend? 
A. Upon the viscosity (commonly miscalled the "thickness") 
of the liquid ; upon the roughness, material and diameter of the 
pipe ; the pressure, etc. 

Q. When long lines of pipe are used, should the diameter of the 
pipe be the same all the way along, or should there by sections 
be decreasing diameter, as the distance from the pump increases? 
A. Most emphatically, the pipe diameter should remain constant 
clear out to the end. 



HANDBOOK ON ENGINEERING. 575 

TAKING CARE OF A PUMP. 

Q. What can be said about taking care of a pump? A. In 
places where an inferior grade of labor is employed, oil and dirt 
are sometimes found covering the steam chest and pump to the 
depth of an inch in thickness ; stuffing boxes are allowed to go 
leaky and get loose ; the valve motion is never looked after ; lost 
motion is never taken up, and the pump will be let run in a slip- 
shod way for months, until some accident occurs. This will 
sometimes exist in places where the engine is well taken care of. 

Q. Should not as good care be taken of a steam pump as of 
an engine? A. Yes. It is a steam engine, and the fact that it 
has generally but little adjustability, should not render it liable to 
lack of care. 

Q. What is a very common thing for pump runners to do when 
anything happens? A. To condemn the pump at once without 
finding out the cause of the trouble. 

Q. What is one reason of this? A. The man who understands 
an ordinary engine, will often become quite perplexed when he 
examines the steam end of a direct acting steam pump, because 
he does not comprehend the principal feature of its construc- 
tion — that all direct acting steam pumps which have no fly 
wheels and cranks, must generally have an auxiliary piston in 
order to carry them over the " dead center." A direct acting- 
steam pump is really a double engine ; a plain, flat slide valve 
admitting steam to a small piston, which in turn operates the 
main valve, which gives steam by the usual arrangement to the 
main piston. 

Q. What would save firemen and engineers much trouble with 
jsteam pumps ? A. If they would take the trouble to examine 
their pumps carefully, and find out the way their valves were 
Arranged and actuated. 

Q. Upon what does the successful performance of a pump 



576 HANDBOOK ON ENGINEERING. 

depend, in great measure? A. Upon its proper selection from 
among the many patterns differing from each other in size, pro- 
portion and general arrangement. 

Q. What may be said about the selection of pumps? A. 
Pumps are often selected improperly for their work. As an illus- 
tration, a man who wishes to use a circulating pump for a surface 
condenser, where the water pressure upon the pump cylinder will 
never exceed 5 to 10 pounds, will buy a pump intended for boiler 
feed work, and having its steam cylinder about three times the 
area of its pump cylinder. 

Q. What will be the result in such a case? A. There will be 
little or no pressure in the steam cylinder when working on the 
condenser ; and while there is pressure sufficient to move the 
main piston, there is not enough to operate the auxiliary piston 
with positiveness. 

Q. In ordering a pump, or in asking estimates, 'what informa- 
tion should be given? A. In ordering a pump, it is to the inter- 
est of the purchaser to fully inform the maker or seller on the 
following questions : 1st. For what purpose is the pump to be 
used? What is the average steam pressure? 2d. What rs the 
liquid to be pumped ; and is it hot or cold, clear or gritty, fresh, 
salt, alkaline or acidulous? 3d. What is the maximum quantity 
to be pumped per minute or hour? 4th. To what height is the 
liquid to be lifted by suction, and what is the length of the suction 
pipe, and the number of elbows or bends? 5th. To what height 
is the liquid to be pumped, and what is the length of discharge 
pipe ? 

Q. How can an engineer familiarize himself with the direction 
of the auxiliary steam and exhaust passages? A. By means of 
a piece of wire. 

Q. What is the special thing to look after in duplex pumps? 
A. That all packings are adjusted uniformly on both sides. 

Q. What would be the result of having the packings different 



HANDBOOK ON ENGINEERING. 077 

upon the two sides of a duplex pump? A. The machinery would 
run unsteadily. 

Q. If a pump works badly, what should be about the first thing 
to look at? A. The connections. 

Q. When a pump is first connected, what should be done? 
A. It should be blown through to remove dirt ; if it be of the 
class which will permit of removing the bonnets and blowing 
through, that should be done. 

Q. What pump piston speed is recommended for continuous 
boiler feeding service? A. About 50 feet per minute. 

Q. What may be said about the care and use of steam pumps 
of all kinds? A. It is important that the pump be properly and 
thoroughly lubricated ; that all stuffing-box, piston and plunger 
packings be nicely adjusted ; not so tight as to cause undue fric- 
tion ; nor so slack as to leak badly. 

Q. In which end of a steam-pumping machine is there most 
likely to be trouble? A. In the water end. 

Q. If a pump slams and hammers in its water end, is it neces- 
sarily defective in its water cylinder? A. No; it may be that 
there is no suction chamber, or not enough ; or sometimes it slams 
because the suction pipe is not large enough. 

Q. What are very common defects in cheap grades of pumps ? 
A. Too little valve area in the pump end; too great lift for the 
valves. 

Q. What are the principal causes of pumps refusing to lift 
water from the source of supply? A. Among these may be 
mentioned leaky suction pipes, worn out pistons, plungers, pack- 
ings or water valves ; rotten gaskets on joints in piping or pump ; 
and sometimes a failure to properly prime the pump as well as 
the suction pipe. 

Q. What is one great cause of a pump refusing to lift water 
w£ien first started? A. It often happens that a pump refuses to 
lift water while the full pressure against which it is expected to 

37 



578 HANDBOOK ON ENGINEERING. 

work is resting upon the discharge valves, for the reason that the 
air within the pump chamber is not dislodged, but only compressed, 
by the motion of the plunger. It is well, therefore, to arrange 
for running without pressure until the air is expelled and water 
follows ; this is done by placing a valve in the delivery pipe 
and providing a waste delivery, to be closed after the pump has 
caught water. 

Q. Sometimes when starting, the water may not come for a 
long time ; what is the best thing to do in this case? A. First, 
open the little air cock, which is generally located in the top of 
the pump, between the discharge valves and the air chamber, to 
let off any accumulation of air which may there be confined 
under pressure. Very often, by relieving the pump of this air 
pressure, it will pick up its water by suction and operate 
promptly. 

Q. What precaution must be taken in priming the pump? A. 
The air cock, which should be provided at the top of the pump, 
should be opened to allow the escape of the air from the suction 
pipe and from the pump, and then the valve in the priming pipe 
should be opened. The pump should then be started slowly, as 
it aids in more completely filling the pump cylinders, which 
otherwise, might not occur and the pump might fail to lift water. 

Q. Is there any advantage in having air in the suction? A. 
Sometimes a small amount of air let into the suction will cause less 
jarring when the duty is very heavy. 

Q. What may be said about pumping hot water? A. Where 
the hot water is very hot, it should gravitate to the pump, instead 
of an attempt being made to draft it. 

Q. In the plunger pumps, what is about the only wearing part 
of the water end? A. The packing of the plunger stuffing-boxes. 

Q. How can a pump be prevented from freezing? A. By 
having draining cocks and opening them when the pump is 
idle. 



HANDBOOK ON ENGINEERING. hl$ 

Q. What may be said about leather piston packing for water 
cylinders? A. For cold water, or sandy, gritty water, the 
leather packing has many points to commend it ; it makes a 
tight piston, and one that is the least destructive to pump 
cylinders. 

Q. What is the best way to handle the square packing mostly 
employed, which is composed of alternate layers of cotton and 
rubber? A. Cut the lengths a trifle short, then there will be 
room for the packing to swell and not cause too much friction. I 
have known pistons where this precaution has not been taken to 
be fastened so securely in the cylinder by the swelling of the dry 
packing, that full steam pressure could not move them. 

Q. What is the remedy in such a case? A. Remove the 
follower, take out the different layers of packing and shorten their 
lengths. 

Q. What is the reason that some soft waters corrode pipes so 
often? A. Because they contain a large proportion of oxygen. 

Q. Will a pump with a 6" water cylinder and a 6" steam cylin- 
der force water into a boiler, the discharge from water cylinder 
being 4" diameter; boiler pressure, 80 lbs.? A. A pump with a 
6" water cylinder and 6" steam cylinder will not force water into 
the boiler which supplies it, no matter what the steam pressure, 
nor what the size of discharge pipe. It will not move. The 
pressures would be equalized and there would be nothing to over- 
come friction of steam and water in pipes and cylinder. The 
foregoing case supposes that the water is to be lifted to the pump ; 
or at least that there shall be no head; also, that there shall be 
no fall from pump to boiler. If there were sufficient head or fall 
to overcome all the various frictions, and no lift, the pump 
would apparently work ; but really, the water piston would be 
dragging the steam piston along. 

Q. How may acids be pumped? A. By what is known as 
blowing up ; that is, by employing a pump to put pressure upon 



580 HANDBOOK ON ENGINEERING. , 

the acid in a closed vessel, thereby forcing it through a pipe 
placed in the bottom of the vessel. 

Q. In case any wearing part of a pump gets to cutting, what 
should be clone? A. If it is not practicable to stop the pump nor 
to reduce its speed, the part which is getting damaged should be 
given very liberal oiling. 

Q. What is the best oil for this purpose? A. That depends on 
the nature of the cutting surfaces, and on the pressure therein; 
the mineral oils are generally more cooling than others, although 
they have less body to resist squeezing. 

CALCULATING THE BOILER FOR A STEAM PUMP. 

The amount of work which a boiler has to do is very easy of 
determination. Given the largest number of gallons which a 
pump will be required to pump per minute, and the height in feet 
from the surface of the well from which the water is drawn, to 
the point of discharge, you can easily tell by multiplying by 8| — 
the weight in pounds of one gallon — the number of foot pounds 
of power consumed per minute in lifting the- water, adding a cer- 
tain percentage for friction of the machine and of water in the 
pipe, we have the total number of foot pounds consumed per 
minute, and this divided by 33,000 will be the horse power 
consumed. 

The allowance for friction will vary with the style, size and 
condition of the pump, the size of the pipe, and, above all, the 
manner in which the pipe is connected up, the number of right 
angle turns, etc. 

This may be arrived at in another way. A column of water 
2.3 feet in height exerts a pressure of one pound. Allowing the 
.3 for friction, we can, by dividing the total left in feet by two, 
get at the pressure per square inch, which is being exerted against 
the water piston or plunger, and multiplying by the number of 



HANDBOOK ON ENGINEERING. 581 

square inches in that piston gives the total pressure against which 
the pump is working. This multiplied by the piston speed in feet 
minutes, and divided by 33,000, will give the lift in horse power. 
In this case, as in the other, the lift must be calculated from the 
surface of the supply, and not from the pump, when the pump is 
lifting its supply. If the water flows to the pump it must be 
calculated from the height of the water cylinder. An allowance 
of, say, 25 per cent, should be made above the horse power thus 
shown, in order to provide for contingencies, and to be on the 
safe side. 

In selecting- a boiler to do this work, it must be borne in mind 
that a boiler which is sold for a certain horse power, is supposed 
to be able to furnish that power in connection with a good steam 
engine , and they are not apt to be overrated . Now , the steam pump 
as usually built, does not approach in economy the ordinary steam 
engine, and, therefore, a boiler which will develop twenty-five 
horse power in connection with a good engine would be too small 
for a pump which was required to do the same amount of work. 
The evaporation of 30 pounds of water per hour from feed at 100 
degrees Fahr. into steam of 70 lbs. pressure, has been adopted by 
several authorities as a horse power. Any good automatic cut-off 
will run on this amount of water, and if an estimate can be made 
of the comparative performance of the pump under consideration, 
a close approximation to the desired size of boiler can be made. 

THE WORTHINGTON WATER METER. 

The counter registers cubic feet ; one foot being T-^ gallons, 
United States standard. It is read in the same way as registers 
of gas meters. The following example and directions may be of 
use to those unacquainted with the method: If a pointer is 
between two figures, the smaller one must invariably be taken. 
Suppose the pointers of the dials to stand as in the engraving. 



582 



HANDBOOK ON ENGINEERING. 



The reading is 6,874 cubic feet. From the dial marked ten wc 
get the figure 4 ; from the next, marked hundred, the figure 7 ; 
from the next, marked thousand, the figure 8 ; from the next, 




marked ten thousand, the figure 6. The next pointer being | 
between ten and 1, indicates nothing. By subtracting the read- 
ing taken at one time, from that taken at the next, the consump- 
tion of water for the intermediate time is obtained. 

TABLE OF PRESSURE DUE TO HEIGHT. 









O) 




0) 












03 




03 




u 




u 




u 




u 




u 




^ 




Fh 




. 




. 




. 




. 




. 




13 . 




. 




£ A 








£ -^ 




fS ^ 




w -P 




w J 




$ -3 




m O 




« 2 




S ° 




X « 




JS » 








nS O 


d 


u 3 
ft"" 1 


-d 


ft"! 


d 


2 s 
ft"! 


•d 


ft"! 


•d 


ft"! 


■d 


g| 


■d 


ft" 




d" 


03 


a 1 


1 03 


w ! 


oS 


a> 


(3 




03 


d 1 


03 


j§J 


& 




A 




J) 












xJ 




£ 






o3 U 




CS '^ 




oS S* 




o3 5h 




03 ^ 




o3 ^ 




03 Jh 




p 03 




53 03 




fl © : 




P 53 




P a> 




p 03 




p 2 


03 


& ft 


© 


o 1 ft 


! « 


jy ft 




a- ft 




C< ft 




& ft 


03 


eft' 


fe 


H 


fe 


3 


|fe 


H 


Em 


H 


£ 


H 


Eh 


H 


ft 


H ! 


1 


0.43 


15 


6.49 


30 


12.99 


45 


19.49 


60 


25.99 


75 


32.48 


90 


38.96 


5 


2.16 


20 


8 66 


35 


15 16 


50 


21.65 


65 


28 15 


80 


34 65 


95 


41 If 


10 


4 33 


25 


10.82 


| 40 


17.32 


55 


23.82 


70 


30 32 


85 


36.82 


100 


43 .1 































HANDBOOK ON ENGINEERING. 



583 



TABLE OF DECIMAL EQUIVALENTS OF 8ths, 16ths, 
32ds AND 64ths OF AN INCH. 



8ths. 


32ds. 


64ths. 


64ths. 


J = .125 


.i 


_ 


.03125 




.015625 


3.5 


.546875 


I = .25 


-A- 





.09375 




.046875 


3JL 


.578125 


| = .375 


.5. 


= 


.15625 


A = 


.078125 


1! = 


.609375 


h = .50 


* 





.21875 


JL. 


.109375 


ii 


.640625 


| = .625 


= 


.28125 


-9 


.140625 


H = 


.671875 


I = .75 


11 


= 


.34375 


11 


.171875 


itz 


.703125 


I ^= .875 


& 


= 


.40625 


13 


.203125 


.734375 




15 


— 


.46875 


15 


.234375 


49 


.765625 




ii 


= 


.53125 




.265625 


51 


.796875 


I6ths. 


19 
3 2 


= 


.59375 


IS 


.296875 


tt = 


.828125 




21 


= 


.65625 


t\ = 


.328125 


H = 


.859375 


A- = -0625 


23 


= 


.71875 


23 


.359375 


SlL 


.890625 


A = 1875 


H 


= 


.78125 


If = 


.390625 


tt = 


.921875 


YV = .3125 


2i 


= 


.84375 


tt = 


.421875 


s_i _ 


.953125 


f 6 - == .4375 


Is 


— 


.90625 


It = 


.453125 


1! = 


.984375 


tV = .5625 


3 1 


— 


.96875 


11 = 


.484375 






H = -6875 








.515625 






ff = .8125 
















[f = .9375 

















LATENT HEAT OF LIQUIDS, UNDER A PRESSURE 
OF 30 INCHES OF MERCURY. 

(TREATISE ON HEAT, BY THOMAS BOX.) 



Latent Heat 
in Units. 



Increase of Tempe- 
rature of Liquid, 
if Heat had not 
become Latent. 



iiVater 

Ucohol 

Sther 

_>il of Turpentine. 
Naphtha 



966 

457 
313 

184 

184 



966° 

735° 

473° 

390° 

443° 



Regnault. 
Ure. 



The Boiling Point of different Liquids varies ; and the Boiling Point 
)f a liquid varies with the pressure. 



584 



HANDBOOK ON ENGINEERING. 



f 


3554 

3910 
4265 
4621 
4976 
5332 
5687 
6042 
6398 
6753 
7108 


o 


SHlQa«(OOB3NH^ 
CO CO I'M— <— lOOffiOOOON 


<4H 

OS 


00>ONC5'aNOJ«iCOO5!£l 
CC^M05NiONOQO'OCO 


^ 


Cl(>iOci5H©t*>OCOHOO 






000'j3tHNON®-*«0 
OOOM-*->DCDO-iKl>ON 



lOHOOif-N^ONWO 
CDQ0O5— <CO"*COCOOi>-tCO 



05COI>-iiOffl«i500-*CCi 



-nQ05Mh--HCO'*00N 
'*COQ0^CO<X>Q0'-ICO»Ci00 

NC005-*0©«NCOQO-* 
lOCOWt-QOOOOiOJOO" 
OrH«05<#ir5i»NO)OH 
,H_|^hi-Ii-H,-I.-i,-<— l(NCv| 

OOt^COiO^COtN— l OiQ0'-X> 

-HOOrHiOOOOlOOONWQO 

N«COO}0-hHNCOCOt)< 



43 £ * 



b- CO CO OS OS r 



c<) c© cs <M 



b- oo <x> co 



TOOOnSOi 



«5 t--*© 



*Sao 
» o OS 

3 o *>> 



3*°" 

--5ft 



wdS 1 



HANDBOOK ON ENGINEERING. 



585 



CAPACITY OF SQUARE CISTERNS IN U. S. GALS. 



5X5 


5X6 


5X7 


5X8 
1496 


5X9 


5X10 


^X6 


6X7 


1 
6X8 6X9 


6X10 


5 ft.. 


935 


1122 


1309 


1683 


1870 


1346 


1571 


1795 2020 


2244 


54 ft.. 


1028 


1234 


1440 


1645 


1851 


2057 


1481 


1728 


1975 2221 


2469 


6 ft.. 


1122 


1346 


1571 


1795 


2019 


2244 


1615 


1885 


2154 2423 


2693 


64 ft.- 


1215 


1459 


1702 


1945 


2188 


2431 


1750 


2042 


2334 2625 


2917 


7 ft.. 


1309 


1571 


1833 


2094 


2356 


2618 


1884 


2199 


2513 2827 


3142 


74 ft.. 


1403 


1683 


1963 


2244 


2524 


2800 


2019 


2356 


2693 3029 


3366 


8 ft.. 


1496 


1795 


2094 


2393 


2693 


2992 


2154 


2513 


2872 ! 3231 


3592 


84 ft. . 


1589 


1907 


2225 


2543 


2861 


3179 


2288 


2670 


3052 3433 


3816 


9 ft.. 


1683 


2020 


2356 


2693 


3029 


3366 


2423 


2827 


3231 3635 


4041 


94 ft.. 


1776 


2132 


2487 


2842 


3197 


3553 


2558 


2984 


3412:3837 


4265 


10 ft.. 


1870 


2244 


2618 


2992 


3366 


3470 


2692 


3142 


3591(4039 


4489 




6X11 


6X12 


7X7JX8 


7X9 


7X10 


7X11 


7X12 


8X8j8X9 




5 ft. . 


2468 


2693 


1832 2094 


2356 


2618 


2880 


3142 


2394 2693 




54 ft. . 


2715 


2962 


2016 2304 


2592 


2880 


3168 


3456 


2633 2962 




6 ft.. 


2962 


3231 


21992513 


2827 


3142 


3456 


3770 


2872 3231 




64 ft.. 


32 09 


3500 


2382 2722 


3063 


3403 


3744 


4084 


3112.3500 




7 ft.. 


3455 


3770 


2565 2932 


3298 


3665 


4032 


4398 


3351 3770 




74 ft.. 


3702 


4039 


2748 3141 


3534 


3927 


4320 


4712 


3590 4039 




8 ft.. 


3949 


4308 


2932 3351 


3770 


4189 


4608 


5026 


3830 4308 




84 ft.. 


4196 


4577 


31153560 


4005 


4451 


4896 


5340 


4069 4578 




9 ft.. 


4443 


4847 


3298 3769 


4341 


4712 


5184 


5655 


4308 4847 




94 ft.. 


4689 


5116 


3481 3979 


4576 


4974 


5472 


5969 


4548 


5116 




10 ft.. 


4936 


5386 


3664' 4 188 


4712 


5236 


5760 


6283 


4788 


5386 





WEIGHT OF WATER. 



1 cubic inch 03617 pound. 

J2 cubic inches 434 pound. 

1 cubic foot (salt) 64.3 pounds. 

1 cubic foot (fresh) 62.425 pounds. 

I cubic foot 7.48 U. S. Gallons. 

Note. — The center of pressure of a body of water is at two-thirds 
;he depth from the surface 

To find the pressure in pounds per square inch of a column of water, 
'Multiply the height of the column in feet by .434. Every foot elevation 
s called (approximately) equal to one-half pound pressure per square 
inch. 



586 



HANDBOOK ON ENGINEERING. 



SHOWING U. S. GALLONS IN GIVEN NUMBER OF 
CUBIC FEET. 



Cubic 
j^eet. 


Gallons. 


Cubic 

Feet. 


Gallons. 


Cubic Feet. 


Gallons. 


0.1 


0.75 


50 


374.0 


9,000 


67,324.6 


0.2 


1.50 


60 


448.8 


10,000 


74,805.2 


0.3 


2.24 


70 


523.6 


20,000 


149,610.4 


0.4 


2.99 


80 


598.4 


30,000 


224,415.6 


0.5 


3.74 


90 


673.2 


40,000 


299,220.7 


0.6 


4.49 


100 


748.0 


50,000 


374,025.9 


0.7 


5.24 


200 


1,496.1 


60,000 


448,831.1 


0.8 


5.98 


300 


2,244.1 


70,000 


523,636.3 


0.9 


6.73 


400 


2,992.2 


80,000 


598,441.5 


1 


7.48 


500 


3,740.2 


90,000 


673,246.7 


2 


14.9 


600 


4,488.3 


100,000 


748,051.9 


3 


22.4 


700 


5,236.3 


200,000 


1,496,103.8 


4 


29.9 


800 


5,984.4 


300,000 


2,244,155.7 


5 


37.4 


900 


6,732.4 


400,000 


2,992,207.6 


6 


44.9 


1,000 


7,480.0 


500,000 


3,740,259.5 


7 


52.4 


2,000 


14,961.0 


600,000 


4,488,311.4 


8 


59.8 


3,000 


22,441.5 


700,000 


5,236,363.3 


9 


67.3 


4,000 


29,922.0 


800,000 


5,984,415.2 


10 


74.8 


5,000 


37,402.6 


900,000 


6,732,467.1 


20 


149.6 


6,000 


44,883.1 


1,000,000 


7,480,519.0 


30 


224.4 


7,000 


52,363.6 






40 


299.2 


8,000 


59,844.1 







From the above any cubic feet reading can readily be converted into 
U. S. gallons, as follows: 

How many gallons are represented by 53,928 cubic feet? 
50,000 cubic feet — 374,025.9 gallons. 



3,000 


" " = 22,441.5 " 


900 


" " = 6,732.4 " 


20 


" u = 149.6 " 


8 


u " = ■ 59.8 " 


53,928 cubic feet =. 403,409.2 gallonSo 



HANDBOOK ON ENGINEERING. 



587 



SHOWING COST OF WATER AT STATED RATES 
PER lOOO GALLONS. 



Number 

of 

Cubic 

Feet. 






COST PER 


1000 GALLONS. 






5 


6 


8 


10 


15 


20 


25 


30 


Cents. 


Cents. 


Cents. 


Cents. 


Cents. 


Cents. 


Cents. 


Cents. 


20 


$0 007 


$0,009 


$0,012 


$0,015 


$0,021 


$0,030 


$0,037 


$0,045 


40 


0.015 


0.018 


0.024 


0.030 


0.045 


0.060, 


0.075 


0.090 


60 


0.022 


0.027 


0.036 


0.045 


0.066 


0.090' 


0.112 


0.135 


80 


0.030 


0.036 


0.048 


0.060 


0.090 


0.120 


0.150 


0-180 


100 


0.037 


0.049 


0.060 


0.075 


0.111 


0.150 


0.187 


0.224 


200 


0.075 


0.090 


O.f20 


0.150 


0-225 


0.299 


0.374 


0.449 


300 


0.112 


0.135 


0.180 


0.224 


0.336 


0.449 


0-561 


0.673 


400 


0.150 


0.180 


0.239 


0.299 


0.450 


0.598 


0-748 


0.898 


500 


0.188 


0.224 


0.299 


0.374 


0.564 


0.748 


0-935 


1-122 


600 


0.224 


0.269 


0.359 


0.449 


0.448 


0.898 


1.122 


1-346 


700 


0-262 


0.314 


0.419 


0.524 


0-786 


1.047 


1-309 


1-571 


800 


0.299 


0.350 


0.479 


0.598 


0-897 


1.197 


1-496 


1-795 


900 


0.337 


0.404 


0.539 


0.673 


1.011 


1 346 


1.683 


2-020 


1,000 


0-374 


0.449 


0.598 


0-748 


1.122 


1.496 


1.870 


2.244 


2,000 


0.748 


0.898 


1.197 


1.493 


2.244 


2.992 


3-740 


4-488 


3,000 


1.122 


1.346 


1-795 


2-244 


3.366 


4.488 


5-610 


6-732 


4,000 


1.496 


1.795 


2-393 


2.992 


4.488 


5.984 


7.480 


8.976 


5,000 


1.870 


2.244 


2-992 


3-740 


5.610 


7.480 


9-350 


11-220 


6,000 


2.244 


2.692 


3-590 


4-488 


6.732 


8.976 


11.220 


13-464 


7,000 


2.618 


3-141 


4.189 


5.236 


7.854 


10.472 


13-090 


15.708 


8,000 


2.992 


3.590 


4-787 


5-984 


8.976 


11.968 


14.961 


17-953 


9,000 


3.366 


4.039 


5-385 


6.732 


10-098 


13.464 


16.831 


20-197 


10,000 


3.74 


4.488 


5-984 


7-480 


11.122 


14.961 


18.701 


22-441 


20,000 


7.48 


8.976 


11.968 


14.961 


22.443 


29.992 


37-402 


44.882 


30,000 


11.22 


13.46 


17.95 


22-44 


33.664 


44.88 


56.10 


67-32 


40,000 


14.96 


17.95 


23-94 


29.92 


44.885 


59.84 


74-10 


89.77 


50,000 


18.70 


22.44 


29.92 


37.40 


56.103 


74.80 


93.50 


112.20 


60,000 


22.44 


26.92 


35.90 


44.88 


67-323 


89.76 


112.20 


134.64 


70,000 


26.18 


31-41 


41.89 


52-36 


78.543 


104.72 


130.90 


157-08 


80,000 


29.92 


35.90 


47-87 


59.84 


89.766 


119.68 


149.61 


179.53 


90,000 


83.66 


40.39 


53.85 


67.32 


100.986 


134 64 


168-31 


201.97 


100,000 


37.40 


44.88 


59.84 


74.80 


111-22 


149.61 


187-01 


224.41 


200,000 


74.81 


89.76 


119.68 


149.61 


224.43 


299 22 


374.02 


448-82 


300,000 


112.20 


134.64 


179.53 


224.41 


336.64 


448.83 


561.03 


673-24 


400,000 


149.61 


179.53 


239.37 


299.22 


448 -85 


598 . 44 


748.05 


897-66 


500,000 


187.01 


224.41 


299.22 


374.02 


561-03 


748.05 


935.06 


1122.07 


600,000 


224.41 


269-29 


359.06 


448 83 


673-23 


897.66 


1122.07 


1346.49 


700,000 


261.81 


314.18 


418.90 


523.63 


785-43 


1047.27 


1309.08 


1570.88 


800,000 


299-22 


359.06 


478.75 


598.44 


897-66 


1196 88 


1496-10 


1795.32 


900,000 


336.62 


403.94 


538-59 


673.24 


1009-86 


1346.49 


1683.11 


2019.73 


1,000,000 


374.02 


448.83 


59S.44 


748.05 


1122.06 


1498.10 


1870.12 


2244.15 



588 





1-1 S3 


HANDBOC 


)K O^ 


I" 


ENGINEERING. 

■••••••• -in ;©•© •-* • |-~ © -* CO CO 00 

;;;■■••■•©•© : © •© 2 15 § S CO 2 > 

• • • • • j • • '• o © • © ' © • © CO © © © | 




p 
















"o.036 

"o'oii 

' '6 123 

"'6.188 
267 
365 
472 
593 
0.730 




fl 
















"o'oi7 

' '0.062 

"o'.m 

"6.234 

"0362 
515 
697 
0.910 




£3 o 












• •© 

: :° 


0.02 

o'63 

0.04 
0.08 
0.13 
0.20 
0.29 
0.38 
0.49 

63 
0.77 

1 11 


as 

8 

Q 


2 o 
fl 












0.03 
0.04 
0.05 
0.06 
07 
0.09 
0.18 
0.32 
0.49 

70 
0.95 

1 23 


CO© 

fl 

«£>•§ 

fl 




i ; 








07 
0.09 
0.12 
16 
20 
25 
0.53 
0.94 
1.46 
2.09 










05 

""o.'io 

0.17 
0.26 
0.37 

0.50 
65 
0.S1 
0.96 
2 21 
3.88 




7 

W 


fl 






• -OS 

; ;© 


33 

""0.'69 

1.22 
1.89 
2.66 
3 65 
4.73 
6.01 
7.43 


: : : 


cC§ 

fl 

fl 




© ; 
© 


35 
74 
1.31 
1.99 
2.85 
3.85 
5.02 
7.76 
11.2 
15 2 
19.5 
25.0 
30.8 






CO 




© • 


0.81 
1 80 

3 20 

4 89 
7.0 
9.46 

12.47 
19.66 
28.06 




3U 


a 


;© ;© 


3i 

© 


1.60 

"2!44 

5.32 
9.46 
14.9 
21.2 
28 1 
37 5 






. : : | 




HCT 

fl 


0.12 
0.47 
0.97 

1 66 

2 62 

3 75 
5.05 
6.52 
8 15 

10.0 
22.4 
39 












■"" fl 


0.31 

1 05 

2 38 
4.07 
6 40 
9.15 

12.4 
16 1 
20.2 
24.9 
56.1 








: ': : :::::::::: : : : 




J5 

fl 

fl 


84 
3.16 
6 98 
12 3 
19.0 
27.5 
37 
48.0 








; 1 1 j ; 11 




3.3 
13 

28.7 
50 4 
78.0 








:::..:::::.: : II 


JOll 


nnjiu 
•Sl«£) 


ooiffc 




c- '" 


© io © w 


o 
c 


■_- q 


I-© IT 
rHC-l<N 




350 
400 
450 
500 
750 
1000 
1250 
1500 
1750 
2000 
2250 
2500 
3000 


3500 
4000 
4500 
5000 



HANDBOOK ON ENGINEERING. 



589 



SHOWING HOW WATER MAY BE WASTED. 

GALLONS DISCHARGED PER HOUR THROUGH VARIOUS SIZED ORIFICES 
UNDER STATED PRESSURES. 



a 


•a o 

rj rj CD 


Diameters of Orifices in 


Inches and Fraction 


s of an 


Inch. 


























Po 
press 
squar 


4 


1 


k 


& 


$ 


1 


H 


1* 


H 


2 


inch 


inch 


inch 


inch 


inch 


inch 


inch 


inch 


inch 


inch 


20 


8.66 


300 


720 


1260 


1920 


2760 


4920 


7380 


11100 


15120 


19740 


40 


17.32 


450 


960 


1800 


2760 


3960 


6720 


10920 


15720 


21360 


27960 


60 


25.99 


540 


1200 


2160 


3480 


4800 


8580 


13380 


19200 


26220 


34260 


80 


34.65 


620 


1380 


2460 


3840 


5580 


9840 


15480 


22260 


30300 


39540 


100 


43.31 


690 


1560 


2760 


4320 


6240 


11040 


17280 


24900 


33900 


44280 


120 


51.98 


780 


1780 


3000 


4740 


6840 


12120 


18960 


27240 


37440 


48480 


140 


60.64 


816 


1860 


3300 


5100 


7320 


13020 


20160 


29460 


39080 


52320 


150 


64.97 


840 


1920 


3420 


5280 


7620 


13560 


21180 


30480 


41460 


54120 


175 


75.80 


900 


2040 


3660 


5700 


8220 


14640 


22800 


32880 


44940 


58560 


200 


86.63 


960 


2220 


3900 


6120 


8760 


15600 


25020 


35880 


47880 


62580 


235 


101.79 


1080 


2460 


4320 


8S80 


11160 


17100 


26760 


38520 


52260 


68460 



The pressure or head of water is taken at the orifice, no allowance 
being made for friction in the pipe. In practical calculations to deter- 
mine the height which water can be thrown, the head consumed by the 
friction of the water in flowing from the source to the orifice must be 
considered. 



IGNITION POINTS OF VARIOUS SUBSTANCES. 

Phosphorus ignites at . 150° Fahr. 

Sulphur <•' " . 500° " 

Wood " " 800° " 

Coal " " 1000° 

Lignite, in the form of dust, ignites at 150° 

Cannel Coal, " " " " 200° 

Coking Coal, " Ci '.< « 250° 

Anthracite, " " " "....... 300° 



590 



HANDBOOK ON ENGINEERING. 



CONTENTS IN CUBIC FEET AND IN U. S. GALLONS. 

(from trautwein) 

Of 231 cubic inches (or 7.4805 gallons to a cubic foot) ; and for one foot of length of 
the cylinder. For the contents for a greater diameter than any in the table take 
quantity opposite one-half said diameter, and multiply it by 4. Thus, the number 
of cubic feet in one foot length of a pipe 80 inches in diameter is equal to 
8.728X4=34 912 cubic feet. So also with gallons and areas. 





© 


For 1 foot in 






For lfoot in 




O 


For 1 


foot in 


fl 




len 


gth. 


c 




length. 


c 


fl«8 


length. 


.2 © 

05 -S 


©<4-l 


®~i 


© 


si 


**&£ 


© 


j§ © 
ojja 


©<w 

®2 


+?**'•» 


© 


1.2 

5 


il 

© 




Ifl 

!§§ 

o 


ii 


3s£ 

.So 

OS 


S 03 © 

.232 


as? 
© © 




3 


•2 1 

t3 


O ej © 

sis 

^ as as 


00J 



I 


.0208 


.0003 


.0026 


1 


.5625 


.2485 


1 859 


19. 


1 583 


1 969 


14.73 


5-16 


.0260 


.0005 


.0040 


7. 


.5833 


.2673 


1 999 


i 


1.625 


2 074 


15 52 


§ 


-0313 


.0008 


.0057 


| 


.6042 


.2868 


2 144 


20. 


1.666 


2.182 


16.32 


7 -IB 


• 0365 


0010 


.0078 


.6250 


.3068 


2.295 


1 


1.708 


3.292 


17.15 


i 


■ 0417 


.0014 


.0102 


i 


.6458 


.3275 


2.450 


21 


1 750 


2 405 


17 99 


9-16 


.0469 


.0017 


.0129 


8. 


6667 


.3490 


2.611 


i 


1.792 


2.521 


18.86 


I 


.0521 


0021 


.0159 


i 


.6875 


.3713 


2 777 


22. 


1 833 


2.640 


19.75 


11-16 


• 0573 


.0026 


0193 


I 


.7083 


.3940 


2 948 


i 


1.875 


2.761 


20.65 


§ 


.0625 


.0031 


.0230 


1 


. 7292 


.4175 


3.125 


23 " 


1.917 


2.885 


22.58 


13-16 


• 0677 


0031 


.0270 


9. 


.7500 


.4418 


3 305 


1 


1.958 


3 012 


31.53 


| 


.0729 


.0042 


0312 


i 


.7708 


.4668 


3 492 


24. 


2.000 


3 142 


23.50 


15-16 


.0781 


.9048 


0359 


k 


.7917 


.4923 


3 682 


25. 


2.083 


3.409 


25.50 


1. 


• 0833 


0055 


.0408 


I 


.8125 


.5185 


3.879 


26. 


2.166 


3.687 


27.58 


l 


.1042 


.0085 


.0638 


10. 


.8333 


.5455 


4 081 


27. 


2 250 


3.976 


29 74 


1 


.1250 


-0123 


.0918 


i 


8542 


.5730 


4.286 


28. 


2 333 


4.276 


31.99 


I 


.1458 


.0168 


1250 


h 


.8750 


.6013 


4.498 


29. 


2 416 


4 587 


34.31 




.1667 


.0218 


.1632 


I 


.8958 


.6303 


4.714 


30 


2.500 


4.909 


36.72 


2 i 


.1875 


.0276 


.2066 


11. 


.9167 


.6600 


4.937 


81. 


2 583 


5.241 


39.21 


.2083 


.0341 


.2550 


l 


.9375 


.6903 


5.163 


32. 


2 666 


5 585 


41.78 


! 


.2292 


.0413 


3085 


I 


9583 


.7213 


5 395 


33. 


2.750 


5 940 


44.43 


3. 


.2500 


.0491 


.3673 


3. 


.9792 


.7530 


5.633 


34 


2.833 


6.305 


47.17 


i 


.2708 


.0576 


.4310 


12.* 


1 Foot. 


.7854 


5.876 


35. 


2.916 


6.681 


49.98 


i 


.2917 


.0668 


.4998 


i 


1.042 


.8523 


6 375 


36. 


3 000 


7.069 


52.88 


1 


.3125 


.0767 


.5738 


13. 


1.083 


.9218 


6.895 


37. 


3.0S3 


7.468 


55.86 


4. 


.3333 


.0873 


.6528 


£ 


1.125 


.9940 


7.435 


38 


3 166 


7.876 


58.92 


1 


.3542 


.0985 


.7370 


14. 


1.167 


1 069 


7.997j 


39. 


3 250 


8 296 


62.06 




.3750 


.1105 


.8263 


| 


1.208 


1.147 


8.578J 


40. 


3.333 


8.728 


65.29 




.3958 


1231 


.9205 


15. 


1.250 


1.227 


9.180 


41. 


3.416 


9.168 


68.58 


5. 


.4167 


.1364 


1.020 


2 


1.292 


1.310 


9.801 


42. 


3.500 


9.620 


71.96 


k 


.4375 


.1503 


1.124 


16. 


1.333 


1.396 


10.44 


43 


3.583 


10.084 


75.43 


3 


.4583 


1650 


1.234 


h 


1.375 


1.485 


11.11 


44. 


3 666 


10.560 


79 00 


1 


.4792 


.1803 


1.349 


17. 


1.417 


1.576 


11.79 


45. 


3.750 


11.044 


82 62 


6. 


.5000 


,1963 


1.469 


i 


1.458 


1 670 


12.50 


46. 


3.833 


11.540 


86.32 


£ 


.5208 


.2130 


1.594 


18." 


1.500 


1.767 


13.22 


47. 


3.916 


12.048 


90.12 


h 


.5417 


.2305 


1.724 


» 


1.542 


1.867 


13.97 


48. 


4.000 


12.566 


94.02 



HANDBOOK ON ENGINEERING. 591 



CHAPTER XX. 
THE INJECTOR AND INSPIRATOR. 

The energy of motion of a body is well known to be the prod- 
uct of its mass by the half square of its velocity ; hence, it is 
possible to communicate to a body of little weight a large amount 
of energy by moving it fast enough, and in fact, the energy of 
motion would only be limited by the speed which can be given 
the body. In this way a small weight of steam flowing from an 
orifice into a properly shaped jet of water is condensed, while the 
velocity of the steam is greater than if flowing into air ; the 
energy thus communicated is made sufficiently great by increasing 
the weight of steam, which can be done by increasing the area of 
the steam way, until we find such jet pumps adapted to many 
purposes. There are, however, two which are of interest to us 
in this connection, the well-known injector and inspirator, with 
the large family of lifting and non-lifting varieties, all differing 
in details as to form of nozzles, area of passages, distances 
between nozzles, and that class of instruments in which, after a 
certain energy and velocity have been reached, the operation is 
repeated. These might be called " consecutive " instruments. 
The illustrations in this book show some of the simplest and 
adjustable kinds. Within a few years the principle of increase of 
energy by increase of mass or velocity has been applied by in- 
creasing the mass of steam used until we find that not only can a 
few pounds weight of steam put into a boiler a good many more 
pounds of water at a much higher temperature than it had, but 
that in a non-condensing engine it is possible, by using the ex- 
haust in part, to put into the boiler at a much higher pressure 



592 HANDBOOK ON ENGINEERING. 






and temperature, a weight of water which is still greater than 
that of the steam moving it. 

When the injector first made its appearance it was, by many, 
considered as almost a paradox, especially by those who looked 
at the question as one of hydrostatics only. That steam from a 
boiler could put water back into it at the same pressure, and over- 
come the friction of the passages without the aid that a steam 
pump had of a difference of piston areas, was to them a puzzle. 
The use of exhaust steam at atmospheric pressure for the purpose 
of putting water into a boiler at a pressure of 150 lbs. per square 
inch, would be to such minds utterly incomprehensible. The use 
of an injector and inspirator, has this to recommend them, that 
the feed-water cannot be introduced into the boiler cold or nearly 
so, but must be warmed by contact with the steam, and the value 
of this has been already shown. In small boilers where no heater 
is used, an exhaust injector is better than a pump, and so is an 
ordinary injector ; but the former includes in itself an exhaust 
heater, saving a portion of heat from the exhaust, besides taking 
the power as heat also ; while, with the common injector, the 
heat for power and raising temperature are both derived from the 
live steam in the boiler. The latter portion of heat is, of course, 
directly returned to the boiler without loss, but that for power is 
necessarily expended. As to the amount of power used by pump 
and injector compared with each other, it would seem that the 
pump is most efficient. There have been many comparative trials 
of pump and injector, but the results have usually been unsatis- 
factory from contained discrepancies. 

RANGE OF THE INSPIRATOR AND INJECTOR. 

The steam pressure at which an injector will start and the 
highest steam pressure at which it will work constitute what is 
termed the " range " of an injector, and the inspirator varies with 
tne vertical lift and the temperature of the feed water. 



HANDBOOK ON ENGINEERING. 



593 



It must also be borne in mind that the same style of construc- 
tion in an injector and inspirator, while it confines them to about a 
specific range between its lowest starting and highest working points, 
permits of variation as to what the lowest starting point shall be. 
A style of construction which gives a range (on say a 2-foot lift) 
of 25 lbs. to 155 lbs. would permit of a range of o5 lbs. to 1(55 
lbs. (in* fact, to a little higher than 165 lbs.). Different manu- 
facturers, therefore, vary as to the starting point in their stand- 
ard machines — aiming to cover the range which they deem most 
desirable. Nearly all have adopted about 25 lbs. on a 2-foot lift, 
as lowest starting point. 




The World. 



POSITIVE OR DOUBLE TUBE INJECTORS. 

As before stated, this class of injector is provided with two sets 
of tubes or jets, one set adapted to lift the water and deliver it to 



594 HANDBOOK ON ENGINEERING. 



By this 



the second set, which forces the water into the boiler. By 1 
arrangement, it is apparent that inasmuch as the lifting jets 
supply a proportionate amount of water with varying steam pres- 
sures, a wider range is obtainable than with an automatic in- 
jector. In the following cases, it is better to use the double tube 
injectors : — 

1. Where the feed water is of too high a temperature to be 
handled by the automatic injectors. 

2. When a great range of steam variation is accompanied by 
the condition of a long lift. 

The World Injector is one of the best and most popular of the 
double tube type of injectors. It is entirely self contained. It 
is supplied even with its own check valve and operated entirely 
by a single lever,' a quarter of a turn of which starts the lifting, 
after which the completion of the single revolution sets the injector 
working to boiler. 

GENERAL SUGGESTIONS FOR PIPING=UP INJECTORS AND 
INSPIRATORS AND SUGGESTIONS THAT SHOULD BE 
CAREFULLY FOLLOWED WHEN MAKING PIPE CONNEC= 
TIONS. 

Steam. — Connect steam pipe with highest parts of boiler and 
never connect with a steam pipe used for any other purpose. I 
would recommend a globe valve being placed in the steam pipe 
next to boiler which can be closed in case it is desired to take off 
the injector. At all other times it can be left open. When the 
steam connection is made, be sure and take off the injector before 
the steam is turned on the machine.. Then blow out the steam 
pipe with at least forty pounds steam, which will remove all dirt 
and scale. 

Suction* — This pipe must be tight, and if there is a valve in it 
the stem must be well packed. 

To test the suction pipes for leaks, plug up the end of the pipe 



HANDBOOK ON ENGINEERING. 



595 



and then screw on a common iron cap on the overflow ; or if you 
do not have one, unscrew cap X, and place a piece of wood on 
top of valve P ; replace the cap and the wood will hold the valve 
from rising ; then turn on the steam which will locate all lea,ks. 




All pipes, whether steam, suction or delivery, must be of the 
same or greater size than the corresponding branch of each injec- 
tor. Have all piping as short and as straight as possible, and 
especially avoid short turns. 



596 HANDBOOK ON ENGINEERING. 

If any old pipe is used, see that it is not partially filled or 
stopped up with rust. 

If the injector or inspirator has to lift the water very high or 
draw it very far, have the suction pipe a size or two larger than 
called for by the suction branch of the injector or inspirator. 

Have the water supply (suction) pipe independent of any other 
connection. The suction pipe must be absolutely air tight ; the 
slightest leak, in most cases, will prevent the injector or inspirator 
from forcing water into the boiler. 

Always place a globe valve in the suction pipe as close to the 
injector as possible, and place it so that it will shut down against 
the water side and see that the stem is packed tight. 

When using the injector or inspirator as non-lifting, put two 
globe valves in the suction, one close to the injector, the other as 
far from it as you can conveniently, keeping the one farthest from 
the injector or inspirator tolerably close throttled. This will 
surely repay you for your trouble. The check valve may be next 
to boiler with a valve between it and boiler, the further from 
injector the better. If the injector forces through a heater, place 
check valve between injector and heater. Also place a valve 
between heater and check valve so you can take check valve out 
if necessary. 

Size of pipes* — If injector or inspirator has over 10 feet lift, 
or a long draw, use suction pipe from strainer to valve a size 
larger than the connection on injector, reducing when you reach 
the valve. 

In all other cases, use for all pipes same size as injector 
connection. 

Blow-off* — Always blow out steam thoroughly before con- 
necting injector, so as to remove any dirt, rust or scale that 
may be in the pipes. 

Caution. — The suction pipe must be absolutely tight I 
throughout. To make sure that it is so, test the suction as directed. 



HANDBOOK ON ENGINEERING. 597 

DIRECTIONS FOR CONNECTING AND OPERATING THE 
HANCOCK INSPIRATOR. 

** Stationary n Pattern* — Connect as shown by cut above 
steam, suction and delivery. For full instructions, see page 588. 

For a lift of 5 ft., 15 lbs. steam pressure is required. 
" ik 10 " 20 " " " " 

15 " 25 < k " " 

20 " 35 " " 
25 " 45 " 

Operation* — Open overflow valves Nos. 1 and 3 ; close forcer 
steam valve No. 2 and open the starting valve in the steam pipe. 
When the water appears at the overflow, close No. 1 valve ; open 
No. 2 valve one-quarter turn and close No. 3 valve. The inspir- 
ator will then be in operation. 

Note. — No. 2 valve should be closed with care to avoid damag- 
ing the valve seat. When the inspirator is not in- operation, both 
overflow valves Nos. 1 and 3 should be open to allow the water to 
drain from it. No adjustment of either steam or water supply is 
necessary for varying steam pressures, but both the temperature 
and quantity of the delivery water can be varied by increasing or 
reducing the water supply. The best results will be obtained 
from a little experience in regulating the steam and water supply. 
If the suction pipe is filled with hot water, either cool off both it 
and the inspirator with cold water, or pump out the hot water by 
opening and closing the starting valve suddenly. To locate a leak 
in the suction pipe, plug the end, fill it with water, close No. 3 
valve and turn on full steam pressure. Examine the suction pipe 
and the water will indicate the leak. If the inspirator does not 
lift the water properly, see if there is a leak in the suction pipe. 
Note if the steam pressure corresponds to the lift as above speci- 
fied, and if the sizes of pipe used are equal in size to inspirator 
connections. If the inspirator will lift the water, but will not de- 
liver it to the boiler, see if the check valve in the delivery pipe is 



598 



HANDBOOK ON ENGINEERING. 



in working order and does not " stick." Air from a leak in the 
suction connections, will prevent the inspirator from delivering 
the water to the boiler, even more than it will in lifting it only. If 
No. 1 valve is damaged, or leaks, the inspirator will not work 
properly. No. 1 valve can be easily removed and ground. 

THE HANCOCK STATIONARY INSPIRATOR. 





Suction. 



Overflow. 

To remove scale and deposits from inspirator jets or parts, 
disconnect the inspirator and plug both the suction and delivery 
outlets with corks. Open No. 2 valve and fill the inspirator with 
a solution of one part muriatic acid and ten parts water . Allow 
this solution to remain in the inspirator over night, then wash it 
thoroughly in clear water. 

Note. — It is not generally necessary to return an inspirator 
for repairs. The repair parts required can be ordered and the 
inspirator readily put in order. 



HANDBOOK ON ENGINEERING. 599 

TO DISCOVER CAUSE OF DIFFICULTIES. 

WHEN INJECTOR FAILS TO GET THE WATER. 

1. The supply may be cut off by : (a) Absence of water at the 
source, (b) Strainer clogged up. (c) The suction pipe, hose 
or valve stopped up ; or if a hose is used, its lining may be loose 
(a frequent cause of trouble). 

2. A large leak in the suction (note that a small leak will pre- 
vent injector from working, but not from getting the water). 

3. Suction pipe or water very hot. Open drip-cock, turn 
steam on slowly, then shut it off quickly. This will cause the 
cool air to rush into the suction pipe and cool it off. Repeat if 
necessary. 

4. Lack of steam pressure for the lift ; or, in some instances, 
too much steam pressure. If the steam pressure is very high, the 
injector will get the water more readily if the steam is turned on 
slowly and the drip-cock left open until the water is got. 

IF THE INJECTOR GETS THE WATER BUT DOES NOT FORCE IT TO 
THE BOILER. 

1. No globe valve on the suction with which to regulate the 
water, or else the supply water not properly regulated. 

2. Dirt in delivery tube. 

3. Faulty check valve. 

4. Obstruction between injector and check valve, or between 
check valve and boiler. 

5. Small leak in suction pipe admitting air to the injector 
along with the supply water. It is ten to one this is the cause of 
the difficulty every time. 

6. Be sure you understand the directions for starting before 
you condemn the injector. • 



600 



HANDBOOK ON ENGINEERING. 



IF THE INJECTOR STARTS BUT Li BREAKS." 

1. Supply water not properly regulated. If too much water, 
the waste or overflow will be cool ; if too little, the water will be 
very hot. 

2. Leaky supply pipe admitting air to the injector. It is ten 
to one this is the cause of difficulty. The suction must be air 
tioht ; test as directed. 



MODE OF 
CONNECTING 




The above illustration shows the mode of connecting the Pen- 
berthy Injector. 

3. Dirt or other obstruction, such as lime, etc., in delivery 
tube. 

4. Connecting steam pipe to pipe conducting steam to other 
points besides the injector, or not having suction pipe inde- 
pendent. 



HANDBOOK ON ENGINEERING. 



601 



5. Sometimes a globe valve is used on the suction connection 
that has a loose disc, and after starting the disc is drawn down, 
thus partially closing the valve ; it is, of course, equivalent to 
giving the injector too little water. To remedy this, take the 
globe valve off and reverse it end for end. 

To clean* — To clean injector, unscrew plug 0, and the re- 
movable jet Y (which rests in it) will follow the plug out. 
Turn on steam (not less than forty pounds) and all dirt will be 
blown out. Examine all passages and drill holes and see that no 
dirt or scale has lodged in them. Replace jet by setting it in the 
plug (which acts as a guide) and screw into place tightly. Be 
c ireful not to bruise any jets, and use no wrenches on body of 
injector, 

PRICE LIST, CAPACITY, HORSE POWER, ETC* 



Pipe Connections. 



Capacity per Hour. 

1 to 4 ft. lift, 50 to 75 

lbs. Pressure. 



Horse 
Power. 







Steam. 


Suction. 


Delivery, 


Maximum. 


Minimum. 




oo. . 


$16 00 


3 

f 


F 


§ in- 


SO gal. 


55 gal. 


4 to 8 


A 


18 00 


4 " 


120 " 


70 " 


8 to 10 


4 A ...... 


'20 00 




i 




165 " 


90 " 


10 to 15 


B 


25 00 


a 


1 


1 " 


250 •' 


135 " 


15 to 25 


13 li . 


30 00 


| 


2 


a << 


340 " 


165 " 


25 to 35 


C 


40 00 


1 




• 1 " 


475 " 


300 " 


35 to 50 


cc. 


45 00 


1 




1 " 


575 " 


350 " 


50 to 60 


D ... . 


55 00 


11 




li " 


750 " 


4'!0 " 


60 to 95 


DD ... 


60 00 


u 


n 


1* " 


' 920 " 


500 " 


95 to 162 


E 


75 00 


H 




1| " 


1300 " 


700 " 


120 to 150 


KK .... 


90 00 


Is 




1| " 


1740 " 


900 " 


165 to 230 


F 


110 00 


2 


2 


2 " 


2270 " 


1100 " 


230 to 290 


FF 


125 00 


2 


2 


2 


2820 " 


1400 " 


290 to 365 



To test for leaks. — Plug up end of water supply pipe, then 
lit a piece of wood into cap Z, so that when screwed down it will 
hold the valve P in place, then turn on steam and it will locate 
leak. Do not fail to do this in case of any trouble. 



START AND STOP INJECTOR. 



To start. — Open full the globe valve in water supply first, 
and then globe valve in steam pipe wide open. If water issues 
from overflow, throttle the valve H until discharge stops. Reg- 



(302 



HANDBOOK ON ENGINEERING. 



ulate injector with water supply valve, not by steam valve. 
When water supply is above the injector, in starting open steam 
valve first. 

To stop. — Close the steam valve. The water valve H need 
not be closed unless the injector is used as a non-lifter, or lift is 
considerable. 

The following table gives the number of British thermal units in a pound of water 
at different temperatures. They are reckoned above 32 degs. Fah., because, strictly 
speaking, water does not exist below 32 degs. Fah., and ice follows another law. 

WATER BETWEEN 32° AND 212° FAH. 



a> 




J2 


o 




.Q 


© 




CO 


© 




.a 


8. 


2-6 


d ■" 


d 


.-S'O 


d ** 


d 


00 ™J 

^T3 


d *» 


d 


-2-0 


d *" 






a o 


c3 




s o 


«3 


m 


•3 O 




d a 


« o 


<D 


X5 <M 


O 


+* o 

-d ^ 


<y 


*a O 


© 


Ut 


« O 




+= a 


be o 


a 


+3 P< 


kp ■- 




« a 


bp © 




« a 


£P -2 


5 a 


03 u 

B a 


- 0) 


a* 

<U eg 


*-* 

M a 


5 t-t-2 
^ ao 




B a 


£a§ 


£,d 
© « 


© S 

ffla 


> ® d 

> a© 


32° 


0.00 


62.42 


110° - 


78 00 


61.89 


115° 


1'3 26 


61.28 


179° 


147.54 


60 57 


35 


8.02 


62.42 


112 


80 00 


61 86 


146 


114 27 


61.26 


180 


148.54 


60 55 


40 


8.06 


62.42 


113 


81 01 


61.84 


147 


115.2a 


61.24 


181 


149.55 


60.53 


45 


13.08 


62 42 


114 


82.02 


61.83 


148 


116 29 


61.22 


182 


150.56 


60.50 


50 


18.10 


62.41 


115 


83.02 


61 82 


149 


117.30 


61.20 


183 


151 57 


60.48 


52 


20.11 


62 40 


116 


84.03 


61 80 


150 


118 30 


61.18 


184 


152 58 


60.46 


54 


22.11 


62.40 


117 


85.04 


61 78 


151 


119 31 


61.16 


1S5 


153 58 


60 44 


56 


24.11 


62 39 


118 


86 05 


61.77 


152 


120 32 


61.14 


186 


154 59 


60 41 


58 


26.12 


62 38 


119 


87.06 


61 75 


153 


121 33 


61.12 


187 


155 60 


60 . 39 


60 


28 12 


62.37 


120 


88.06 


61 74 


154 


122.34 


61.10 


188 


156 61 


60.37 


62 


30.12 


62.36 


121 


89 07 


61 72 


155 


123.34 


61.08 


189 


157 62 


60.34 


64 


32.12 


62 35 


122 


90.08 


61.70 


156 


124 35 


61.06 


190 


158 62 


60.32 


66 


34.12 


62 34 


123 


91.09 


61.68 


157 


125.36 


61.04 


191 


159.63 


60 29 


68 


36.12 


62.33 


124 


92 10 


61.67 


15S 


126.37 


61.02 


192 


160.63 


60.27 


70 


38. U 


62 31 


125 


93 10 


61 65 


159 


127.38 


61.00 


193 


161.64 


60 25 


72 


40.11 


62.30 


126 


94 11 


61.63 


160 


128 38 


60.98 


194 


162 65 


60 22 


74 


42.11 


62 28 


127 


95.12 


61.61 


161 


129 39 


60.96 


195 


163 . 66 


60.20 


76 


41 11 


32.27 


128 


96.13 


61 60 


162 


130 40 


60.94 


196 


164.66 


60 17 


78 


46 10 


62.25 


129 


97.14 


61.58 


163 


131.41 


60.92 


197 


165.67 


60 15 


80 


48.09 


62.23 


130 


9S 14 


61.56 


164 


132.42 


60.90 


198 


166.68 


60.12 


82 


50.08 


(.2.21 


131 


99 15 


61.54 


165 


133.42 


60.87 


199 


167.69 


60.10 


81 


52.07 


62.19 


132 


100.16 


61.52 


166 


134.43 


60.85 


200 


168.70 


60.07 


86 


54.06 


62 17 


133 


101.17 


61 51 


167 


135.44 


60.83 


201 


169.70 


60.05 


88 


56.05 


62.15 


134 


102 18 


61.49 


168 


136.45 


60.81 


202 


170 71 


60.02 


90 


58 04 


62.13 


135 


103.18 


61.47 


169 


137.46 


60.79 


203 


171 72 


60.00 


92 


60.03 


62 11 


136 


104 19 


61.45 


170 


138.46 


60.77 


204 


172.73 


59.97 


94 


62 02 


62.09 


137 


105.20 


61.43 


171 


139 47 


60.75 


205 


173.74 


59.95 


96 


64 01 


62 07 


138 


10(5.21 


61.41 


172 


140 48 


60.73 


206 


174 74 


59.92 


98 


66 01 


62.05 


139 


107.22 


61.39 


173 


141.49 


60 . 70 


207 


175 75 


59 89 


100 


68.01 


62 02 


140 


108 22 


61.37 


174 


142 50 


60.68 


208 


176 76 


59 87 


102 


70.00 


62 00 


141 


109.23 


61 36 


175 


143.50 


60.66 


209 


177.77 


59.84 


104 


72.00 


61.97 


142 


110 24 


61 34 


176 


144.51 


60.64 


210 


178.78 


59.82 


106 


74.00 


61.95 


143 


111 25 


61 32 


177 


145.52 


60.62 


211 


179.78 


59.79 


. 1C8 


76 00 


61.92 


144 


112.26 


61.30 


178 


146.53 


60.59 


212 


ISO. 79 


59 76 






HANDBOOK ON ENGINEERING. 603 

To find the number of gallons of water delivered by a steam 
pump in one minute, when the diameter and stroke of water 
piston, and the number of strokes per minute are given : — 

Rule* — Square the diameter of water piston and multiply the 
result by .7854. Multiply this product by the stroke of the 
water piston in inches ; and multiply this product by the number 
of strokes per minute, and divide the result by 231. 

Example* — How many gallons of water per minute will a 
steam pump deliver, whose water cylinder is 6 inches in diameter 
and 12 inches stroke, making 60 strokes per minute? 

Ans. 88.128 galls. 

Operation : 6X$X .7854 28.2744. 

28.2744 X 12 X 60 
And, ~j = 88.128. 

To find the relative proportion between the steam and water 
pistons. 

Rule* — Multiply the area of the pump piston by the resistance 
of the water in pounds per square inch ; and divide the product 
by the pressure of steam in pounds per square inch. The quotient 
will give the area of steam piston in square inches to balance the 
resistance. To this quotient add from 30 to 100 per cent of it- 
self, — depending on the speed of the pump, — and divide the 
sum by .7854, and extract the square root of the quotient for the 
diameter of the steam piston. 

Example* — What should be the diameter of the steam piston 
to force water against a pressure of 125 pounds per square inch, 
the diameter of water piston being 6 ins. and the steam pressure 
60 lbs. per square inch? Ans. 10^ inches. 

Operation: 6X6 .7874 = 28.2744 sqr. ins. 

And, 28.2744 X 125 = 3534.3 pounds the total resistance. 

3534.3 
Then, — ^ — == 58.9 square inches the area of steam piston* 



604 HANDBOOK ON ENGINEEKING. 

We will add 50 per cent for friction in pump and in delivery 
pipe, and for a moderate speed of pump. 
Then, 58.9 X .50 = 29.45. 
And, 58.9 + 29.45=88.35. 

88.35 
And, = 112.49 sqr ins. 



Then, a/ 112.49 = 10.6 ins. the diameter of the steam piston. 

To find the pressure against which a pump can deliver water, 
when the diameter of steam piston, pressure of steam in pounds 
per square inch, and diameter of water piston are given : — 

Rule* — Multiply the area of steam piston by the pressure of 
steam in pounds per square inch, and divide the product by the 
area of the pump piston, and deduct from 30 to 50 per cent for 
friction in the delivery pipe and in the pump itself. 

Example* — The area of the steam piston is 112 square inches, 
and the area of water piston -is 28 square inches, and the steam 
pressure is 60 lbs. per square inch, against what pressure can the 
pump deliver water, the resistance from friction being 48 per cent? 

Ans. 125 lbs. per sqr. in., nearly. 

112X60 
Operation : 28 — =240. 

And, 240 X -48 =115.20. 
Then, 240 — 115.20 = 124.8. 

To find the steam pressure required when the diameter of the 
steam piston, the diameter of the water piston, and the resistance 
against the pump in pounds per square inch are given: — 

Rule. — Multiply the area of water piston by the resistance on 
the pump in pounds per square inch, and divide the product by 
the area of the steam piston. 



HANDBOOK ON ENGINEERING. 605 

Example* — The resistance against the pump, including fric- 
tion, is 240 pounds per square inch. The area of steam piston 
is 112 square inches, and the area of water piston is 28 square 
inches. What pressure of steam is required to operate the pump ? 

Ans. 60 lbs. per sqr, in. 

Operation: — — — =60. 
11.4 

Now anything over 60 lbs. will operate the pump, and the faster 
it is run the higher must be the pressure above 60 pounds. 

To find the diameter of water piston when the diameter of 
steam piston, the steam pressure in, pounds per square inch, and 
the resistance against the pump piston in pounds per square inch 
are given : — 

Rule. — Multiply the area of steam piston in square inches by 
the steam pressure in pounds per square inch, and divide the 
product by the resistance in pounds per square inch on the water 
piston. 

Example* — The resistance against the pump, including fric- 
tion, is 240 pounds per square inch ; the area of steam piston is 
112 square inches, the steam pressure is 60 pounds per square 
inch, what should be the diameter of water piston? 

Ans. 6 inches. 

112 X 60 
Operation : ■ = 35.65 sqr ins. Call it 36 sqr. ins. 

Then, y36~ = 6. 

To find the horse power required in a steam pump to feed a 
boiler with a given number of pounds of water per hour against a 
given pressure of steam : — 

Rule* — Multiply the velocity of flow of water in feet per min- 
ute by the total pressure against which the water is pumped in 
pounds per square inch, and divide the product by 33,000, and 
the quotient will be the horse power. 



606 HANDBOOK ON ENGINEERING. 

Example* — What horse power is required to feed a boiler 
with 600 gallons of water per hour against a total resistance of 
112 lbs. per square inch, including the friction in the delivery 
pipe, lift of water in suction pipe, weight of check valve, and 
friction in the pump itself? Ans. 1 H. P. nearly. 

Operation: 600 X 231 = 138,600 cubic inches of water per 

hour. 

138,600 
And, — ™ — =2310 cubic inches of water per minute. 
60 

2310 
And, -=r— =192.5 feet per minute, the velocity of the 

water. 

The total resistance is 112 lbs. per sqr. in. 
Then, 192.5 X 112 = 21560 foot pounds. 

21560 
And ' 3^000 = - 653H ' P - 

Now add say 50 per cent and we have .653 X .50= .3265. 
And, .653 + .3265 = .9795. 

This pump will feed a boiler as shown above, or it will deliver 
600 gallons of water per hour under a head of 258 feet. 

112 
Thus, —^ = 258. 
' .433 

To find the horse-power of boiler required to furnish steam for 
a pump running at its fullest capacity. 

Rule* — Multiply the number of gallons of water delivered by 
the pump in one minute by 8-J. Multiply this product by the 
total height in feet to which the water is to be lifted, measuring 
vertically from the source of supply to the point of delivery, and 
divide the result by 33,000. Add from 50 to 75 per cent to the 
quotient for loss from friction of water in the pipe, friction in 
the pump, waste of steam in the cylinder, and other contingencies, 
a nd the result will give the horse power of boiler required. 



HANDBOOK ON ENGINEERING. 607 

Example. — What horse-power of boiler is required to run a 
steam pump lifting 800 gallons of water per minute to a height of 
163 ft. from the source of supply? Ans. 50 H. P., nearly. 

Operation ; 800 X 8 J = 6667 lbs. of water. 

And, 6667 X 163 = 1,086,721 footpounds. 
1,086,721 

And ' ~l37000~ =33H - P -' near1 ^ 

Then, 33 X .50 = 16.50. 

And, 33 + 16.5 = 49.5. 

To find the diameter of discharge nozzle for a steam pump, 
when the diameter and stroke of the water piston and the number 
°f strokes per minute are given, and the maximum flow of water 
in feet per minute is given : — 

Rule* — Find the cubic contents of the water cylinder for one 
stroke in cubic feet, and multiply it by the number of strokes per 
minute. Multiply this product by 144 and divide the result by 
the velocity of the water in feet per minute, and the quotient will 
be the area of pump nozzle in square inches. 

Example. — The diameter of water cylinder is 10 inches, and 
the stroke of piston is 12 inches, and the speed is 50 strokes per 
minute. The velocity of water required is 500 feet per Wnute, 
what should be the diameter of pump discharge nozzle? 

Ans. 3 J ins., nearly. 

Operation: 10 X 10 X .7854= 78.54 sqr. ins. area of piston. 

And, 78.54 X 12 = 942.48 cubic inches in the cylinder for one 

stroke. 

942.48 
And, 1woo = .5454 of a cubic foot for one stroke. 

And, .5454 X 50 = 27.27 cubic feet for 50 strokes per minute. 

27.27 X 144 .,''', 

Then, ttt^ == 7.8537 sqr. ins. the area of the nozzle. 

' 500 



[ 7.8537 __ 

NI.7854 



And, — = 3.1 ins. the diameter. 



608 HANDBOOK ON ENGINEERING. 

To find the approximate size of suction pipe when its length 
does not exceed 25 ft. and when there are not more than two 
elbows in the same : — 

Rule* — Square the diameter of water cylinder in inches and 
multiply it by the speed of the piston feet in per minute ; divide 
this product by 200, and divide this quotient by .7854 and 
extract the square root, and the result will be the diameter of 
suction pipe, except for very small pipes when it should be made 
larger than the size given by the rule, in order to lessen the friction 
of the moving water. • 

Example* — The diameter of water cylinder is 6 ins., the stroke 
of piston is 12 ins., and the number of strokes per miuuteis 60, 
what should be the diameter of suction pipe? Ans. 4 ins. 



~ .. 6X6X60 
Operation : ^— = 10.8. 

^00 

And, JM:= 13.75. 
.7854 



Then, a/ 13. 75 = 3.7 ins. The^e is no pipe of this size made, 
so take 4-inch pipe. 

To find the velocity in feet per minute necessary to discharge 
a given number of gallons of water per minute through a straight 
smooth iron pipe of a given diameter, regardless of friction : — 

Rule* — Reduce the gallons to cubic feet and multiply by 144, 
and divide the product by the area of the pipe in square inches. 

Example* — What should be the velocity of the water to dis- 
charge 100 gallons of water per minute through a 4-inch pipe ? 

Ans. 149 ft. per minute, 

~ ^ 100X231 in , .- . , 

Operation : — — j- — = 13 cubic feet. 
1 1 28 

And, 13 X 144 = 1872 cubic inches placed in a continuous 
line. 

Then, 4 X 4 X .7854 = 12.5664 square inches, the area of 
pipe. 

A , 1872 1/1Q 

And, = 149. 

12.5664 






HANDBOOK ON ENG INEKRING. 609 

To find the velocity in feet per minute of water flowing through 
a pipe of given diameter, when the diameter of water cylinder and 
speed of piston in feet per minute are given : — 

Rule* — Multiply the area of water cylinder in square inches 
by the piston speed in feet per minute, and divide the product by 
the area of the pipe' in square inches. 

Example* — The diameter of water cylinder is 8 ins., and the 
piston speed is 100 ft. per minute, and the diameter of discharge 
pipe is 4 ins., what is the velocity of the water in the discharge 
pipe? Ans. 400 ft. per minute. 

Operation: 8 X 8 X .7854 = 50.26 sqr. ins. area of the 
water piston. 

And, 50.26 X 100 = 5026. 

The area of the pipe is 12.56 sqr. ins. 

„, 5026 , An 

Then, =400. 

12.56 

To find the number of gallons of water discharged per minute 
through a circular orifice under a given head : — 

Rule*— Find the velocity of discharge in feet per second and 
multiply it by 60, then multiply this product by the area of the 
orifice in square feet, and multiply this last product by 7.48, and 
the result will be the gallons discharged per minute. 

Example. — How many gallons of water will be discharged per 
minute through an orifice 4 inches in diameter under a head of 81 
feet? Ans. 2829.7 galls. 

Operation: V^^ 9 - And > 9 X 8.025 == 72.225 feet per 
second, the velocity of discharge. The factor 8.025 is a con- 
stant for any head, and is found thusly: — 



v '2 X32.2 =8.025. 

Or, the velocity of discharge may be found in this manner : --— 



^2 X 32.2 X 81 = 72.22 feet per second, that is, the veloc- 
ity in feet per second equals the square root of the acceleration 

39 



BIO HANDBOOK ON ENGINEERING . 

due to gravity multiplied into the head in feet. Continuing the 
operation, we have : — 

72.225 X 60 — 4333.5 feet per minute. 

And, 4 X 4 X .7854 = 12.5664 sqr. ins. area of orifice. 

And, — ' =.0873 of a square foot,, the area of orifice, 

144 

also. 

Then, 4333.5 X .0873 i=h 378.3 cubic feet. 

And, 378.3 X 7.48 = 2829.7 galls. 

Note. — With a ring orifice only 64 per cent of the above 
amount of water would be discharged, and with a funnel-shaped 
orifice only 82 per cent. 

To find the number of gallons of water discharged per minute 
under a given pressure in pounds per square inch : — 

Rule. — Divide the given pressure in pounds per square inch 
by .433 in order to get the head in feet, and then proceed accord- 
ing to the foregoing rule. 

Example* — ■ How many gallons of water will be discharged per 
minute through an orifice one square inch in area, under a pres- 
sure of 35.073 lbs. per square inch? Ans. 81 galls, per minute. 

35.073 
Operation: — J^~ = 81 ft., head equivalent to the given 

pressure. 

And, V2X32.2 X81 = 72.225 ft. per second the velocity. 

And, 72.225 X 60 = 4333.5. 

Also, YI1 = -00694 of a square foot, equals the area of the 

orifice. 

And, 4332.5 X .00694 = 30.07449. 
And, 30.07449 X 7.48 = 224.9 galls. 
Then, deducting 64 per cent, we have: — 
224.9 X .64= 143.9. 
And, 224.9 — 143. y =81. 

/ 



HANDBOOK ON ENGINEERING. 611 

To find the area of orifice in square ins. necessary to discharge 
a given number of gallons of water per minute under a given 
head in feet : — 

Rule* — Divide the number of gallons by the constant number 
15.729 multiplied into the square root of the head, and the result 
will be the area of orifice in square inches. 

Example* — What must be the area of orifice to discharge 
1778.5 gallons of water per minute under a head of 81 feet? 

AnSo 12.56 sqr. ins. 

Operation : V 8 1 = 9 . 

And, 9 X 15.729 = 141.6. 

1778.5 
Then, -—-=::= 12.56. 
' 141.6 

To find how many gallons of water will flow through a straight 
smooth iron pipe in one minute under a given pressure in pounds 
per square inch, or head in feet : — 

Rule* — Multiply the inside diameter of the pipe in feet by the 
head in feet, and divide the product by the length of pipe in feet. 
Extract the square root of the quotient and multiply it by 48, 
and the product will be the velocity of flow in feet per second. 
Multiply this result by 12 to reduce it to inches, and by 60 for 
the flow per minute, and multiply again by the area of the pipe in 
square inches, and divide by 231 for the gallons discharged per 
minute. 

Example* — How many gallons of water will be discharged per 
minute through a 4-inch pipe 2000 feet long, under a head of 92 
feet? Ans. 230 galls, per minute. 

Operation : 4 ins. — .33 of a foot. 

And, 92 X .33 = 30.36. 

30.36 
And ' 2000" = -° 15 ' 



612 HANDBOOK ON ENGINEERING. 

And, V^015 =.1225. 

Then. .1225 X 48 X 12 = 70.56 ins. per second. 

And, 70.56 X 60 =4233.60 ins. per minute. 

Then, 4 X 4 X .7854 — 12.56 sqr. ins. the area of the pipe. 

And, 4233.60 X 12.56 =53174.016 cubic ins. 

53174.016 
Then, — ^31 = 230.2. 

Example* — Assume two wells A and B with their mouths on 
a level. Well A is 26 ft. deep, and well B is 40 ft. deep. Well 
A is fed by natural springs and has a depth of water of 5 feet. 
The distance between the wells is 600 feet. How many gallons 
of water will a 1 inch pipe, laid perfectly straight and level, 
syphon over in one minute providing well B is always pumped 
dry, and that the pipe extends into well A 26 feet, and into well 
B 38 feet, using bends instead of elbows? 

Ans. 4 galls, per minute. 

Operation* — The head equals 38 feet. 
The diameter of the pipe equals .0833 foot. 
Then, 600 + 38 + 26 = 664 ft. total length of pipe. 
And, 38 X .0833 = 3.1654. 

3.1654 
And ' -664~- = - 0047 - 



And, V -0047 = .068. 

Then, .068 X 48 = 3.264 ft. velocity per second. 

And, 3.264 X 60 = 195.840 ft. velocity per min. 

The area of pipe equals .7854 sqr. inch. 

Then, 195.840 X .7854 = 153.8127. 

And, 153.8127X7.48 = 1150.52. 

1150.52 
And, — r.-7 — = 8 nearly, gallons. 



HANDBOOK ON ENGINEERING. 613 

Deducting 50 per cent on account of 2 bends and friction, we 
have 4 gallons per minute syphoned over. 

To find the head in feet due to friction in a pipe running 
full : — 

Rule* — Multiply the length of the pipe in feet by the square 
of the number of gallons per minute, and divide the product by 
1,000 times the 5th power of the diameter of the pipe in inches. 
The quotient less 10 per cent is the head in feet necessary to over- 
come the friction. 

Note. — The head is the vertical distance from the surface of 
the water in the tank or reservoir, to the center of gravity of the 
lower end of the pipe, when the discharge is into the air, or, to 
the level surface of the lower reservoir when the discharge is under 
the water. 

Example. — "A 2-inch pipe 100 feet long and running full, 
discharges 50 gallons of water per minute, what is the head in 
feet due to friction? Ans. 7.029 feet. 

Operation: 2 X 2 X 2 X 2 X 2 = 32 = the 5th power of the 
diameter of the pipe. 

And, 50 X 50 = 2500. 
And, 2500 X 100=250,000. 
Also, 32 X 1,000 = 32,000. 

250,000 
Then > WOO" = 7 ' 81 ' 

And, 7.81 less 10 percent of itself equals 7.029. 
The resistance to the flow of water in pounds per square inch, 
due to friction, is found by dividing the friction head by 2.3. 

7.029 
Thus, ^-Qg- = 3.05 lbs. 

To find the size of pump required to feed a boiler of a given 
capacity : — 



614 HANDBOOK ON ENGINEERING. 

Rule. — Multiply the number of pounds of water evaporated 
per pound of coal by the number of pounds of coal burned per 
sqr. foot of grate surface per hour, and multiply this product by 
the number of square feet of grate surface in the boiler furnace. 
This will give the number of pounds of water evaporated by the 
boiler in one hour, Divide this by 60 to find the evaporation per 
minute, and divide again by 8-| in order to get the evaporation in 
gallons per minute ; add from 10 to 15 per cent to the last result 
for leakage and other contingencies, and select a pump that will 
deliver the gross number of gallons of water per minute at any 
speed that may be desired, usually taken, however, at 100 feet 
per minute . 

Example* — What should be the dimensions of the water end 
of a steam pump, and what should be the speed of piston to sup- 
ply a boiler having a grate surface of 20 square feet, and burning 
15 pounds of coal per square foot of grate, and evaporating 9 
pounds of water per pound of coal per hour ? 

Operation: 20 X 15 X 9 =2700 pounds of water evapo- 
rated per hour. 

2700 
And, = 45 lbs. of water evaporated per minute. 

And, = 5.4 galls, per minute, 

Then, 5.4 plus 10 per cent of itself, equals 6 galls, nearly per 
per minute. 

Referring to a pump maker's catalogue we find that a single 
pump 3 1" X 2|" X 5", making 90 strokes per minute, will do 
the work, or, a duplex pump 3" X 2" X 3", making 100 strokes 
per minute will do the work equally as well. Again, adding 10 
per cent to the pounds of water evaporated per minute we have, 
45 + 4.5 = 49.5 pounds. And, 49.5 X 27.71 = 1371.64 cubic 
inches displacement in the water cylinder per minute, and at 90 
strokes per minute we have 15.24 cubic inches displacement per 
stroke. 



HANDBOOK OX ENGINEERING. 615 

Thus, ' = 15.24 which is all that is required for our 

90 

boiler. 

Now, taking the above single pump we have: 2.25 X 2.25 X 
.7854 X 5 = 19.8 cubic inches displacement per stroke. And, 
taking the duplex pump we have: 2 X 2 X .7854 X ,3 X 2 — 
18.8 cubic ins. displacement for each double stroke of the piston, 
or, plunger, showing that either pump is of ample capacity to 
feed the boiler at a fair piston speed. 

To find the duty of a pumping engine when the number of 
pounds of coal burned, the number of gallons of water pumped, 
the pressure in pounds per square inch against which the pump 
piston works, and the height of suction are given : — - 

Rule* — Find the head in feet against which the pump works, 
by multiplying the pressure by 2.3, add the suction in feet 
to this head in order to get the total head. Multiply the 
gallons of water by 8-| to get the pounds of water deliv- 
ered. Then multiply the total number of pounds of water 
by the head in feet, and divide the product by the number of 
pounds of coal divided by 100, and the result will give the duty 
in foot pounds. The duty of a pumping engine is the number of 
pounds of water raised one foot high for each 100 pounds of coal 
burned. 

Example* — What is the duty of an engine pumping 2,890,000 
gallons of water in 12 hours against a pressure of 30 pounds per 
sqr. inch, the suction being 12 feet, and coal burned 24,470 
pounds? Ans. 8,070,426 foot pounds. 

Operation: 30 X 2.3 = 70 nearly the head in feet. 

And, 2,890,000 X 8i = 24,083,333 pounds of water. 

Also, 70 + 12 = 82 ft. total lift of water. . 

And, 24,083,333 X 82 = 1,974,833,306 lbs. of water lifted 
one foot high in 12 hours. 

Then, 2 -MZ?= 244.7. 
100 



616 HANDBOOK ON ENGINEERING. 

A , 1,974,833,306 Q nf7n AS)a 

And, J ' ' = 8,0/0,426. 

244.7 

To find the horse power of a pumping engine : — 

Rule. — Divide the number of pounds of water raised one foot 
high in one minute by 33,000. 

Example. — What is the H. P. of the pumping engine given 
in the above example? Ans. 83.11 H. P. 

Operation: 12 X 60 = 720 minutes. 

. , 1,974,833,306 „ AQ ' . 1u - . . -. „ . 

And, ~1 - = 2,742,824 lbs. of water raised one foot 

720 

high in one minute . 

Then, 2 ' 742 ' 824 = 83.11. 
33,000 

To find the capacity of a pump to feed a boiler it is necessary 
to know how much water the boiler is capable of evaporating per 
minute or per hour. Each horse power of boiler capacity corre- 
sponds to an evaporation of thirty pounds of water per hour. It 
is good practice to operate a pump slowly and continuously, and 
for this reason the pump running at its normal speed should be 
capable of supplying about twice as much water as the boiler 
evaporates under usual conditions. 

To find the diameter of water cylinder to deliver a certain num- 
ber of gallons of water per minute, when the stroke of the piston 
and the number of strokes per minute are given : — 

Rule. — Multiply the number of gallons by 231, and divide the 
product by the stroke of the piston, and divide this quotient by 
the number of strokes per minute, and divide this last quotient 
by .7854, then extract the square root of the result for the 
diameter of the water piston. 

Example. — A battery of boilers evaporate 100,000 pounds of 
water in one hour, what should be the diameter of water cylinder 
to supply this battery, the stroke of piston being 12 inches and 
making 100 strokes per minute? Ans. 7 inches. 



HANDBOOK ON ENGINEERING. 617 

100,000 
Operation:" — t^k — = 1666^ pounds of water evaporated in 

one minute. 

L666| 
And, ftl = 200 galls, evaporated in one minute. Then 

following the above rule we have : — 

200 X 231 =46200. 

46200 
And, 12 = 3850. 

3850 
And, -jqq- =38.5. 

38.5 
And ' 77854 = 49 * 

Then, j/49 = 7" the required diameter. 

To determine the H. P. of boiler a steam pump of given 
dimensions will supply when the number of strokes per minute 
are given : — 

Rule* — Multiply the area of the piston is square inches by the 
stroke of piston in inches, and this product divided by 231 will 
give the gallons per stroke. Multiply this quotient by the num- 
ber of strokes per minute for the number of gallons per minute, 
and by 60 for the number of gallons per hour. Multiply this 
product by 8i to find the number of pounds of water per hour 
delivered by the pump, and divide this product by 30 for the 
H. P. of boiler the pump will supply. This rule is based upon the 
assumption that the full capacity of the water cylinder is deliv- 
ered at each stroke, no allowance being made for slippage, leak- 
age, or short strokes. 

Example. — - The water piston of a steam pump is 6 inches in 
diameter and has a stroke of 12 inches, making 100 strokes per 
minute, what H. P. of boiler will the pump supply? 

Ans. 2448 H. P. 



618 HANDBOOK ON ENGINEERING. 

Operation: 6 X 6 X .7854 — 28.2744 sqr. ins. area of 
piston. 

And, 28.2744 X -12 == 339.2928 cubic inches for one stroke. 

339.2928 
And, — ^TTi — = 1.4688 oralis, per stroke. 
2 6 1 " l 

And, 1.4688 X 100 = 146.88 galls, per minute. 

And, 146.88 X GO = 8812.8 galls, per hour. 

And, 8812.8 X 8J = 73,440 pounds of water per hour. 

73440 
Then, QA = 2448 H. P. of boilers. 
' 30 

Watt allowed one cubic foot (62 J lbs.) of water per H. P. per 
hour. Then taking this allowance instead of 30 as above, we 

73440 
would have, -a 9 g =1175 H. P. of boilers which the above pump 

would be suitable for, and which could be run very slowly, thus 
prolonging the life of the pump. 

Even though a suction pipe should be perfectly air tight, a 
perfect vacuum cannot be formed in it, because water contains 
air, and even the coldest water gives off some vapor tending to 
impair the vacuum. Twenty-eight feet is a very good lift for a 
pump taking its water by suction. 



HANDBOOK ON ENGINEEK1NG. 



619 



CHAPTER XXI. 
MECHANICAL REFRIGERATION. 

About the first thing asked by persons who are becoming 
interested in the subject of refrigerating and ice-making is, " Tell 
me how the thing is done ? ' ' 

Mechanical refrigeration, primarily, is produced by the evapo- 
ration of a volatile liquid which will boil at low temperature, and 
by means of a special apparatus the temperature and desired 
amount of refrigeration is placed under control of the operator. 



•*^° --•, 

%&£? 



Waste/ /pTP-'^S 

Gas 0^<tf& 




Elemental Refrigerating Apparatus. 
Fie. 1. 



The simplest form of refrigerating mechanical apparatus 
consists of three principal parts: A, an ''evaporator," or, as 
sometimes called, a " congealer," in which the volatile liquid is 
vaporized; B, a combined suction and compressor pump, which 



620 



HANDBOOK ON ENGINEERING 



sucks, or properly speaking, '• aspirates " the gas discharged by 
the compressor pumps, and under the combined action of the 
pump pressure and cold condenser, the vapor is here reconverted 
into a liquid, to be again used with congealer. You now see the 
function of the compressor pumps and condensers. 

PRINCIPLES OF OPERATION. 

The action of all refrigerating machines depends upon well- 
defined natural laws that govern in all cases, no matter what type 
of apparatus or machine is used, the principle being the same in 
all ; while processes may slightly vary, the properties of the par- 
ticular agent and manner of its use affecting, of course, the 
efficiency or economic results obtained. 




Fig. 2. — Outline drawing of mechanical compression system 



OPERATION OF APPARATUS. 

(See Fig - * 2») The apparatus being charged with a sufficient 
quantity of pure ammonia liquid, which we will, for simplicity, 
assume to be stored in the lower part of the condenser 6 y , a small 
cock or expansion valve controlling a pipe leading to the congealer 



HANDBOOK ON ENGINEERING. 621 

or brine tank A, is slightly opened, thus allowing the liquid to 
pass in the same office as a tube or flue in steam boiler and having 
precisely the same function, it may be called heating or 
steam-making service. The amount of water capable of being 
boiled into steam in a boiler depends upon the square feet of heat- 
ing surface, temperature of fire and pressure of steam ; and 
the same is true of the capacity of heating surface pre- 
sented by the coils in the evaporator. The heat is transmitted 
through the coils from surrounding substance to the ammonia 
liquid, which is boiled into a vapor the same as water is boiled 
into steam in a steam boiler; as previously explained, the heat 
thus becomes cooler ; the amount taken up and made negative 
being in proportion to the pounds of liquid ammonia evaporated. 

FUNCTION OF THE PUHP AND CONDENSER. 

The office of the compressor, pump and condenser is to re- 
convert the gas after evaporation into a liquid, and make the 
original charge of ammonia available for use in the same appa- 
ratus, over and over again. It will appear to the reader, after 
having carefully followed the text, that the pump and condenser 
might be dispensed with, but these conditions may only be eco- 
nomically realized when the, at present, expensive ammonia 
liquid can be obtained in great quantities and at less cost than 
the process of reconverting the vapor into a liquid by compression 
machinery and condenser on the spot. 

WHAT DOES THE WORK. 

The real index of the amount of cooling work possible is the 
number of pounds of ammonia evaporated between the observed 
range of temperature. To make the above clear, we will add 
that each pound of ammonia during evaporation is capable of 
storing up a certain quantity of heat, and that the simplest forms 



622 HANDBOOK ON ENGINEERING. 

of refrigerating apparatus might consist, as shown by engraving, 
of two parts, to wit : A congealer and a tank of ammonia. In this 
apparatus the ammonia is allowed to escape from the tank into 
the congealer as fast as the coils therein are capable of evapo- 
rating the liquid into a gas. When completely evaporated the 
resulting vapor is allowed to escape into the atmosphere, which 
means it is wasted, the supply being maintained by furnishing 
fresh tanks of ammonia as fast as contents are exhausted. This 
process, while simple, would be tremendously expensive, costing 
at the rate of about $200 per ton, refrigerating or ice-melting 
capacity. To recover this gas and reconvert to a liquid on the 
spot in a comparatively inexpensive manner, is the object to be 
obtained . 

MECHANICAL COLD EASILY REGULATED. 

This being under the control of the cock or valve leading from 
the condenser (called an expansion valve). As the gas begins to 
form in the evaporator, the compressor pump B is set in motion 
at such a speed as to carry away the gas as fast as formed, which 
is discharged into the condenser under such pressure as will bring- 
about a condensation and restore the gas to the liquid state ; the 
operation being continuous so long as the machinery is kept in 
motion. 

UTILIZING THE COLD. 

To utilize the cold thus produced for refrigerating, two meth- 
ods are in use, the first of which is called the brine system ; the 
second is known to the trade as the direct expansion system, both 
of which I will now proceed to explain at some length. 

BRINE SYSTEM. 

In this method, the ammonia evaporating coils are placed in a 
tank which is filled with strong brine made of salt, which is well 
known not to freeze at temperature as low as zero. This is the brine 



HANDBOOK OX ENGINEERING. 623 

tank or congealer A. The evaporating or expansion of the ammo- 
nia in these coils robs the brine of heat, as heretofore explained, 
the process of storing cold in the brine going on continuously and 
being regulated, as required, at the gas expansion valve. To 
practically apply the cold thus manufactured, the chilled brine or 
non-freezing liquid is circulated by means of a pump through 
coils of pipe which are placed on the ceilings or sides of the apart- 
ments to be refrigerated, the process being analogous to heating 
rooms by steam. 

THE BRINE COOLS THE ROOMS. 

The cold brine in its circuit along the pipes becomes warmer 
by reason of taking up the heat of the rooms, and is finally 
returned to the brine tank, where it is again cooled by the ammo- 
nia coils, the operation, of course, being a continuous one. 

DIRECT EXPANSION SYSTEM. 

By this method, the expansion or evaporating coils are not put 
in brine tanks, but are placed in the room to be refrigerated, and 
the ammonia is evaporated in the coils by coming in direct con- 
tact with the air in the room to be refrigerated, no evaporating 
tank being used. 

RATING OF THE MACHINE IN TONS CAPACITY. 

For the information of the unskilled reader, I will state that 
machines are susceptible of two ratings; that is, either their 
capacity is given in tons of ice they will produce in one day (24 
hours), called ice-making capacity ; or they are rated equal to the 
cooling work done by one ton of ice-making per. day (24 hours), 
called refrigerating capacity. 

DIFFERENCE IN THESE RATINGS. 

Ordinarily the ice-making capacity is taken at about one-half 
of the refrigerating capacity, but this is only approximate, and 



624 



HANDBOOK ON ENGINEERING. 



the tons of ice a refrigerating machine will make depend upon the 
initial temperature of the water to be frozen. 

UNIT OF CAPACITY. 

The unit of capacity is one ton of iee made from water at 32° 
Fahr., into ice at 32°, per day, which is equal to 284,000 lbs. of 
water cooled one degree, or 284,000 heat units, and is the tonnage 
basis for refrigerating capacity as well as ice made from water 
at 32°. 

THE PREPARATION OF BRINE. 



Fig. 1. 

There are two methods in general use, which I will explain. 
Fig. 1 shows one of the methods, which consists of allowing 
water to percolate through a body of salt. 

Take a large water-tight barrel or cask, and lit a false bottom 



HANDBOOK ON ENGINEERING. 6.25 

or wooden grating six or eight inches above the bottom ; this can 
be made of strips of wood about an inch square, and placed not 
over one-half inch apart. This false bottom should be supported 
b} r two strips of boards, each six inches in width, placed on edge 
and nailed to the bottom. These boards should have several holes 
bored near their bottoms to permit a free passage of water. The 
water inlet should be below the false bottom. A single thickness 
of" burlap should be stretched across the top of the false bottom 
and tacked to sides of barrel. The outlet pipe for the brine 
should be four or live inches below the top of the barrel. The 
water is supplied at the bottom from a convenient hose or faucet. 
The supply pipe should be of about 11 in. diameter ; and the 
outlet pipe about li in. diameter. If it is necessary to make 
brine faster than can be accomplished with one barrel, lit up two 
or more extra barrels. To make brine, fill the barrel above the 
false bottom with salt and turn on the water. The salt dissolve s 
rapidly and more must be shoveled in on top. The barrel must 
be kept full of salt or the brine will not be of full strength. No 
stirring is necessary. Keep skimming off all waste matter rising 
to the top. The brine outlet should be provided with a strainer 
of some kind to prevent chips, etc., from running out with the 
brine. Brine should not be made any stronger than is necessary 
to prevent it from freezing. 

Fig"* 2 is the other method of brine-making. This method is 
a water-tight box, say four feet wide, 8 feet long and 2 feet high, 
with perforated false bottom and compartment at end. Locate 
the brine-maker at a point above the brine tank.C onnect the 
space under the false bottom with your water supply, extending 
the pipe lengthwise of the box, being perforated at each side to 
insure an equal distribution of water over the entire bottom surface ; 
use a valve in water supply pipe. Near the top of the brine- 
maker, at end compartment, put in an overflow with large strainer 
to keep back the dirt and salt, and connect with this a pipe, say three 

40 



(526 



HANDBOOK ON ENGINEERING. 



inches in diameter, with salt catcher at bottom, leading into the 
brine tank. Use a hoe or shovel to stir the contents. When all is 
ready, partly fill the box with water, dump the salt from the bags 

<s. Salt Gauge 




Complete Brine Mining Arrangement . 
Fig. 2. 

on the floor alongside and shovel into brine-maker or dump direct 
from the bags into the brine-maker as fast as it will dis- 
solve. Regulate the water supply to always insure the brine 
being of the right strength as it runs into the brine tank. This 
point must be carefully noticed. Filling the brine tank with 
water and attempting to dissolve the salt water directly therein is 
not satisfactory, as quantities of salt settle on the tank bottom 
coils, forming a hard cake. It is a good plan, when desired to 
strengthen the brine, to suspend bags of salt in the tank, the salt 
dissolving from the bags as fast as required ; or the return brine 
from the pumps may be allowed to circulate through the brine- 
maker, keeping same supplied with salt. 

INSULATION OF BUILDINGS. 

The insulation of buildings used for the preservation and 
storage of substances subjected to mechanical refrigeration, is a 



HANDBOOK ON ENGINEERING. 



627 



INSULATING BUILDINGS AND COLD STORAGE ROOHS. 




14. inch Brick 
4 " Air Space 
9 " Brick 
Cement Wash 
Pitched 

2"x.3"Studding 
Tar Paper 
— VT&.G. Board 
— 2"x 4"Studding 
— VJ h. G. Board 
— Tar Paper 
■^I'TifcG. Board 




-14 Brick 

4'' Pitch &• Ashes. 

4" Brick 

4" Air Space 
■14" Brick 




gfe ~ ~ z " jfjELr^d 



36" Brick Wall 
Pitch 

■1" Sheathing 
4" Air Space 
2"x 4"Studding 
T'Sheathing - 
Mineral Wool 
— 2"x 4"Studding 
-1"Sheathing 



Various Aooroved Methods, 



628 HANDBOOK ON ENGINEERING. 

matter of vital importance, when viewed from an economic stand- 
point. It is true that by employment of a large surplus of 
refrigerating power, poor insulation with its entailed great loss 
of negative heat is wastefully overcome, and a certain amount of 
cooling work can be accomplished ; but this is a bad way to reach 
a result; it is like pumping out a leaky ship and keeping ever- 
lastingly at it, when the best way is to stop the leak and be done 
with the pumping — it is a preventable loss. Poor insulation is 
like paying interest on borrowed capital, which is earning nothing 
for the borrower, a never-ceasing and useless drain upon the 
machinery and pocket-book of the user. 

PERFECT INSULATION. 

Perfect insulation is when there is absolutely no transfer of 
heat through the walls of a building ; but this is scarcely pos- 
sible. If it were, once cooling of the contents of a room would 
suffice; for there being no loss, they would continue at the same 
temperature for an indefinite period. If all articles placed in the 
room thereafter were previously cooled to the temperature of the 
room before placing therein, no work need be done thereafter in 
the room itself. A large percentage of the actual work of a 
refrigerating machine is required to make up for transfer of heat 
through the walls, floors and ceilings occasioned by improper 
insulation, and the amount may be experimentally determined 
by proper instruments. Owing to difference in construction, 
exposure and insulation of building, you will find a great dif- 
ference in economy of performance and work done by the 
same machine in use by different parties in the same line of 
business ; and what a given machine and apparatus will do in 
one place is no certain guide for another place somewhat sim- 
ilar ; the insulation, exposure, and method of handling the 
business are mainly responsible for the difference. 



HANDBOOK ON ENGINEERING. 



G29 



As shown by the engraving, screw into the ammonia flask a 
piece of bent one-quarter inch pipe, which will allow a small bot- 
tle to be placed so as to receive the discharge from it. This test 
bottle should be of thin glass with wide neck, so that quarter-inch 
pipe can pass readily into it, and of about 200 centimeters capac- 
ity. Put the wrench on the valve and tap it gently with a ham- 
mer. Fill the bottle about one-third full and throw sample out 
in order to purge valve, pipe and bottle. Quickly wipe off mois- 
ture that has accumulated on the pipe, replace the bottle and open 

ClASSJTUBE 

RUBBER 




Testing for Water by Evaporation. 



valve gently, filling the bottle about half full. This last operation 
should not occupy more than one minute. Remove the bottle at 
once and insert in its neck a stopper with a vent hole for the 
escape of the gas. A rubber stopper with a glass tube in it is 
'the best, but a rough wooden stopper, loosely put in, will answer 
the purpose. Procure a piece of solid iron that should weigh not 
less than eight or ten pounds, pour a little water on this and place 
the bottle on the wet place. The ammonia will at once begin to 
boil, and in warm weather will soon evaporate. If any residuum, 
pour it out gently, counting the drops carefully. Eighteen drops 
are about equal to one cubic centimeter, and if the sample taken 



630 



HANDBOOK ON ENGINEERING. 



amounted to 100 cubic centimeters, you can readily approximate 
the percentage of the liquid remaining. 




Sectional View of io-ton Refrigerating Machine, regular pat- 
tern . Frick Company 's Eclipse Refrigerating Machine, 
with Placer Slide-Valve Throttling Machine. 



LUBRICATION OF REFRIGERATING MACHINERY. 

It is well to speak of this, for the reason that it is an important 
subject; and some users of machinery think that a cheap, low 

29 



HANDBOOK OX ENGINEERING. 631 

grade of oil is really the cheapest. To disabuse their minds of 
this idea and suggest the necessity of high grade oils, both on the 
score of economy and to keep the machinery at all times in 
efficient running order, is the object of this article. First-class 
refrigerating machinery calls for the use of at least three different 
kinds of oil, Nos. 1, 2 and 3, each of high grade: — 

No* t* For use in the steam cylinder, and is known in the trade 
as cylinder oil. This ranges in price from 50c. to $1 per gallon. 
Good cylinder oil should be free from grit, not gum up the valves 
and cylinder, should not evaporate quickly on being subjected to 
heat of the steam, and when cylinder head is removed, a good 
test is to notice the appearance of the wearing surfaces ; they 
should be well coated with lubricant which, upon application of 
clean waste, will not show a gummy deposit or blacken. Use this 
oil in a sight feed lubricator with regular feed, drop by drop. 

No* 2* For use of all bearing and wearing surfaces of machine 
proper — an oil that will not gum, not too limpid, with good 
body, free from grit or acid and of good wearing quality, flowing 
freely from the oil cups at a fine adjustment without clogging, 
and a heavier grade should be used for lubricating the larger 
bearings. 

No. 3* For use in compressor pumps. This oil should be what 
is called a cold test, or zero oil, of best quality. 

Best paraffine oil is sometimes used ; as also a clear West Vir- 
ginia crude oil. This oil, when subjected to a 1ow t temperature, 
should not freeze. 

EFFECTS OF AMMONIA ON PIPES. 

Ammonia has no chemical effect upon iron ; a tank, pipe or 
stop-cock may be in constant contact with ammonia for an in- 
definite time and no action will be apparent. The only protec- 
tion, therefore, that ammonia-expanding pipes require is from 
corrosion on the outer surface. As long as the pipes are covered 



632 HANDBOOK ON ENGINEERING. 

with snow or ice, corrosion does not occur ; the coating of ice 
thoroughly protects thern from the oxidizing effect of the atmos- 
phere ; hut alternate freezing and thawing requires protected sur- 
faces, which are best obtained by applying a coat of paint every 
season. 

Expansion coils having to withstand but a maximum working 
pressure of thirty pounds per square inch, are constructed with 
such absolute security, in whole and in detail, as to make them 
one of the most perfect pipe constructions on a large scale ever 
applied in practice. 




Position of Tank to be Emptied.. 

TO CHARGE THE SYSTEM WITH AMMONIA. 

Position of the tank should be as shown, the outlet valve 
pointing upwards and the other end of the tank raised 12" to 15". 
The connection between the outlet valve of the tank and the 
inlet cock of the system should be a |" pipe. In charging, open 
valve of the tank cautiously to test connection ; if this is tight, 
open valve fully ; start machine and run slowly till tank is empty. 
The tank is nearly empty when frost begins to appear on it; run 
the machine till suction gauge reaches atmospheric pressure. If 
it holds at this pressure when machine is stopped, the tank is 
empty; if not, start up again. In disconnecting, close the valve 
on the tank first, the inlet cock of the system. Weigh tank 



HANDBOOK ON ENGINEERING 



033 



before and after emptying* ; each standard tank contains from 100 
to 110 pounds of ammonia. 

PROCESS OF MECHANICAL REFRIGERATION. 

The process of mechanical refrigeration is simply that of 
removing heat, and mechanism is necessary, because the rooms 
and articles from which the heat is to be removed are already as 
cold, or colder than their surroundings, and consequently, the 
natural tendency is for the heat to flow into them instead of out of 
them. The fact that a body is already cold does not prevent the 
removal of more heat from it and making it still colder. The term 
cold describes a sensation and not a physical property of matter ; 
the coldest bodies we commonly meet with are still possessed of a 
large quantity of heat, part of which, at least, can be abstracted 
by suitable means. The only means by which heat can be 
removed from a body is to bring in contact with it a body colder 
than itself. This is the function that ammonia performs in 
mechanical refrigeration. It is so manipulated as to become 
colder than the body we wish to cool. The heat thus abstracted 
by it is got rid of by such further manipulation that (while still 
retaining the heat it has absorbed) it will be hotter than ordi- 
nary cold water, and therefore, part with its heat to it. Ammonia 
thus acts like a sponge. It sops up the heat in one place and 
parts with it in another, the same ammonia constantly going 
backward and forward to fetch and discharge more heat. The 
complete cycle of operation comprises three parts : — 

1st. A compression side, in which the gas is compressed. 

2d. A condensing side, generally consisting of coils of pipe, 
in which the compressed gas circulates, parts with its heat and 
liquefies. 

3d. An expansion side, consisting also of coils of pipe, 
in which the liquefied gas re-expands into a gas, absorbs heat, 
and performs the refrigerating work. 



b'34 HANDBOOK ON ENGINEERING. 

In order to render the operating continuous, these three sides 
or parts are connected together, the gas passing through them in 
the order named. The liquefied gas is allowed to flow into the 
expansion or evaporating coils, where it vaporizes and expands 
under a pressure varying from 10 to 30 pounds above that of the 
atmosphere, when ammonia is the agent in use. The gas then 
passes into the compressor, is compressed and forced into the 
condensers, where a pressure from 125 to 175 pounds per square 
inch usually exists ; here liquefaction takes place and the re- 
sulting liquefied gas is allowed to flow to a stop-cock having a 
minute opening, which separates the compression from the expan- 
sion side of the plant. The expansion side consists of coils of 
pipe similar to those of the condensing side, but used for the 
reverse operation, which is the absorption of heat by the vapor- 
ization of liquefied gas instead of the expulsion of heat from it, 
as in the former operation. Heat is conducted through the ex- 
pansion or cooling coils to, and is absorbed by, the vaporizing 
and expanding liquefied gas within such coils, for the reason that 
they are connected to the suction or low pressure side of the 
apparatus from which the compressors are continually drawing 
the gas and thereby reducing the pressure in said coils, as already 
stated, to a pressure of 10 to 30 pounds above the atmosphere; 
it being kept in mind that liquefied ammonia in again assuming 
a gaseous condition, has the power or capacity of reabsorbing, 
upon its expansion, a large quantity of heat. The liquefied gas 
entering these coils through the minute openings of the stop-cock, 
above referred to, is relieved of a pressure of 125 to 175 pounds, 
the amount requisite to maintain it in a liquid condition, when it 
begins to boil, and in so doing passes into the gaseous state. To 
do this it must have heat, which can be supplied only from the 
substance surrounding the pipes, such as air, brine, wort, etc. 
As a natural result the surrounding substances are reduced in 
temperature, or cooled. It is apparent from the foregoing that 



HANDBOOK ON 3<:NGTNEERING. 



6o5 




The above is a Sectional Cut of the "Eclipse" Compressor. 



636 HANDBOOK ON ENGINEERING. 

if the expansion coils are placed in an insulated room, that room 
will be refrigerated ; also, if brine or wort is brought in contact 
with the surface of the coils, they also will be reduced in tem- 
perature ; and that brine so cooled can be used to refrigerate an 
insulated room by simply forcing it to circulate through pipes 
or gutters suspended in the same. Either of the above methods 
can be applied to the refrigeration of breweries, packing-houses, 
etc., and for the manufacture of ice, the same gas being used 
over and over again to perform the same cycle of operations. 

THE COMPRESSOR PUMPS. 

The most important feature of a refrigerating machine is the 
compressor pump. To some, the highest efficiency of perform- 
ance (other things being equal, such as proper application and 
proportion of the steam engine dividing the same, with the lowest 
obtainable loss of friction in transmission of power to the 
pump) is the pump which receives the fullest charge of gas 
and most perfectly expels the same ; this is the most efficient 
and will do the most work. 

THE DE LA VERGNE HORIZONTAL COMPRESSOR. 

This compressor is of an entirely new design, embodying all 
the improvements suggested by experience up to date, and having, 
moreover, many original features. 

Particular attention is directed to the following points : — 

The valves are all in the body of the compressor. 

No pipe joints have to be broken to remove the valves or the 
cages. 

The delivery valves are so placed as to allow a free and early 
draining of the cylinder, if liquid should be present. 

The valves are so arranged and provided with such safety 



HANDBOOK ON ENGINEERING. 



637 



devices as to render it impossible for them to get inside the cylin- 
der under any circumstances. 

The stuff ingf-box is effectually sealed, without producing 
undue friction. 











Flat Pipe Coils Suspended from Ceiling on Iron Floors — Beams 
for Storage and Fermenting Rooms. 



DIAGRAM OF DE LA VERGNE SYSTEM. 

The diagram on page 638 is seen to be extremely simple in 
conception ; ammonia, gas and oil are received into the com- 



638 



HANDBOOK ON ENGINEERING. 



pressor, from which they are discharged together into the cooler. 
The cooled oil drops into the first tank while the gas continues 
into the condenser, where it is liquefied and collects in the second 
tank. The liquid ammonia is taken off from a point near the top 
of the second tank. If a little oil is taken over from the conden- 
ser it is conveyed by a pipe, as shown, to a point near the bottom 




^444+H+f 



EXPANSION 
COCK. 



of the second tank, where it remains, since it is heavier than 
liquid ammonia, and cannot rise to get into the liquid pipe of the 
ammonia supply. The liquid ammonia is passed through the 
expansion cock into the expansion coil, where it boils into vapor 
which is drawn off into the compressor to pass around again in 
the order above described. 



RATING MACHINES FOR ICE=nAKING. 

Refrigerating- machines are rated by the effect they produce 
equivalent to the melting of a corresponding amount of ice. Now 
the melting of one pound of ice is equivalent to the absorbing of 



HANDBOOK ON ENGINEERING i 



639 




640 



HANDBOOK ON ENGINEERING 



o 




HANDBOOK ON ENGINEERING. 



641 



142 units of heat. In making ice from water, we have, however, 
to remove more than 142 units. We have first of all to reduce 
the water to 32° before we are ready to produce ice. If the water 
is at 82° this means the removal 50 heat units. Moreover, we 
cannot make ice with economy without going to a temperature 
much lower than 32°. The ice when formed may have a temper- 
ature of 18°, and the specific heat of ice being 0.5 this means the 




iDlAORAH OF THE £>E La VeRGNE IcE'M AKING SYSTEM.' 

The above cut shows, in diagrammatic form, the general outline of 
the process of ice-making with cans. 



removal of 7 more heat units. In other words, we have to 
remove 199 heat units instead of 142 to produce a lb. of ice. 
Thus a 200-ton machine which would easily produce a refrigerat- 
ing effect equal to the melting of 200 tons of ice would only pro- 
duce 142 tons of actual ice. This proportion is still further 
reduced by the inevitable losses attending the use of large freezing 
tanks and the handling of the ice. 

41 



642 



HANDBOOK ON ENGINEERING. 




HANDBOOK ON ENGINEERING. 643 

COHPLETE CYCLE STANDARD DE LA VERGNE VERTICAL 
MACHINE. 

The cut on preceding page shows the engine-room connections 
for the double acting vertical compressor complete with Corliss 
engine. The course of the gas can be very readily followed : 
After being discharged from the compressor it rises to the/o?*e 
cooler, where the oil is cooled and deposited in the pressure tank. 
The ammonia gas goes on to the condenser, which it enters at the 
bottom. As fast as the liquid ammonia collects in the condenser, 
it is drawn off at different levels in the manner already described 
in connection with the condensers. From the storage tank it falls 
into the separating tank, where any remaining oil is trapped, and 
the anhydrous ammonia passes into the rooms to be cooled byway 
of the main liquid pipe. 

The sectional view on following page, represents one of the 
De La Vergne Double Acting Vertical Compressors, as arranged 
for use with oil, as a sealing, lubricating and cooling agent. Two 
passages, marked " suction" and" discharge," respectively, con- 
nect the compressor with the pipe, system. On the up stroke, gas 
flows through the lower suction valve into the space behind the 
moving piston, while the gas above the piston, after being com- 
pressed to the condenser pressure, is discharged through the up- 
per valves (in the loose head) into the discharge passage. On 
the down stroke, gas flows into the cylinder through the upper 
suction valves, and the gas below the piston is compressed and 
passes through the lower discharge valves into the discharge pas- 
sage. The piston in its downward course, closes successively the 
openings of these two discharge valves. When the lower is 
closed, however, the upper one communicates with the chamber 
in the piston, and the gas and oil still remaining below the piston 
are discharged through the valves into the chamber and out by 
the upper discharge valve. The oil being injected directly into 



644 



HANDBOOK ON ENGINEERING. 




HANDBOOK ON ENGINEERING. 645 

the compressor after the compression of the full cylinder of gas 
has commenced, does not reduce the capacity of the machine. 




The above is a cut of the De La Vergne Double Actiug Com- 
pressor, driven by a Corliss Engine. Both the compressor and 
engine cylinder, affording an opportunity of observing the relative 
positions of the pistons in each. 

The oil for " cooling, sealing and lubricating " is brought to 
the compressor by the pipe running along the back of the ' ' A " 
frame. The pipe marked "By-pass" is used when any portion 
of the pipe system in the engine house is to be independently 
exhausted of gas. 



646 HANPBOOK ON ENGINEERING. 



CHAPTER XXII. 






SOriE PRACTICAL QUESTIONS USUALLY ASKED OF EN= 
GINEERS WHEN APPLYING FOR LICENSE. 

Q. If you were called on to take charge of a plant, what would 
be your first duty? A. To ascertain the exact condition of the 
boiler and all its attachments (safety-valve, steam-gauge, pump, 
injector) and engine. 

Q. How often would you blow off and clean your boilers if 
you had ordinary water to use? A. Twice a month. 

Q. What steam pressure will be allowed on a boiler 50" diam- 
eter, -§" thick, 60,000 T. S. ^ of tensile strength factor of safety? 
A. One-sixth of tensile strength of plate, multiplied by thick- 
ness of plate, divided by one-half of the diameter of boiler, gives 
safe working pressure. 

Q. How much heating surface is allowed per horse-power by 
builders of boilers? A. 12 to 15 feet for tubular and flue boilers. 

Q. How do you estimate the strength of a boiler? A. By its 
diameter and thickness of metal. 

Q. Which is the best, single or double riveting? A. Double 
riveting is from 16 to 20 per cent stronger than single. 

Q. How much grate surface do boiler -makers allow per horse- 
power? A. About | of a square foot. 

Q. Of what use is a mud drum on a boiler, if any? A. For 
collecting all the sediment of a boiler. 

Q. How often should it be blown out? A. Three or four times 
a da}^, in the morning before starting, and at noon. 

Q. Of what use is a steam dome on a boiler? A. For storage 
of dry steam. 



HANDBOOK ON ENGINEERING. 647 

Q. What is the object of a safety-valve on a boiler? A. To 
relieve over pressure. 

Q. What is your duty with reference to it ? A. To raise it once 
a day and see that it is in good order. 

Q. What is the use of a check valve on a boiler? A. To pre- 
vent the water from returning back into the pump or injector 
which feeds the boiler. 

Q. Do you think a man-hole in the shell on top of a boiler 
weakens it any? A. Yes, to a certain extent. 

Q. What effect has cold water on hot boilerplates? A. It 
will crack or fracture them. 

Q. Where should the gauge cocks be located? A. The lowest 
gauge cock ought to be placed about 3 inches above the top row of 
flues. 

Q. How would you have your blow-off located ? A. In bottom 
of mud drum or boiler. 

Q. How would you have your check valve arranged? A. With 
a stop cock between check and boiler. 

Q. How many valves are there in a common plunger force pump ? 
A. Two — a receiving and a discharge valve. 

Q. How are they located? A. One on the suction side, the 
other on the discharge. 

Q. How do you find the proper size of safety valves for boil- 
ers? A. Three square feet of grate surface is allowed for one 
inch area of spring-loaded valves, or two square feet of grate 
surface to one inch area of common lever valves. 

Q. G-ive the reasons why pumps do not work sometimes? A. 
Leak in suction, leak around plunger, leaky check valve, or valves 
out of order, or lift too long. 

Q. How often ought boilers to be thoroughly examined and 
tested ? A. Twice a year. 

Q. How would you test them? A. With hammer and with 
hydrostatic test — using warm water. 



648 HANDBOOK ON ENGINEERING. 

Q. Describe the single acting plunger pump ; how it gets and 
discharges its water? A. The plunger displaces the air in the 
suction pipe, causing a vacuum, which is filled by the atmosphere 
forcing the water therein ; the receiving valve closes and the 
plunger forces the water out through the discharge valve. 

Q. What is the most economical boiler feeder? A. An 
Exhaust Injector. 

Q. What economy is there in the Exhaust Injector? A. 
From 15 to 25 per cent saving in fuel. 

Q. Where is the best place to enter the boiler with the feed 
water? A. Below the water level, but so that the cold water can- 
not strike hot plates. If injector is used this is not so material, 
as the feed water is always hot. 

Q. What are the principal causes of priming in boilers? A. 
Too high water, not steam room enough, misconstruction, engine 
too large for boiler. 

Q. How do you change the water in the boiler when steam is 
up? A. By putting on more feed and opening the surface 
skimmer or blow-off valve. 

Q. If the safety valve was stuck how would you relieve the 
pressure on the boiler if the steam was up and could not make its 
escape? A. Work the steam off with engine after covering fires 
heavy with coal or ashes, and when the boiler is sufficiently cool, 
put safety valve in working order. 

Q. If water in boiler is suffered to get low, what may be the 
result? A. Burn top of tubes, perhaps cause an explosion. 

Q. If water is allowed to get too high, what result? A. 
Cause priming, perhaps cause breaking of cylinder head. 

Q. What are the principal causes of foaming in boilers? A. 
Dirty and impure water and animal oil or grease. ' 

Q. How can foaming in boilers be stopped? A. Close throttle 
and keep closed long enough to show true level of water. If that 
level is sufficiently high, feeding and blowing off will usually 
suffice to correct the evil. 



HANDBOOK ON ENGINEERING. 64$ 

Q. What would you do if you should find your water gone 
from sight very suddenly? A. If a light fire draw and cool off 
as quickly as possible ; if a heavy fire cover with wet ashes or 
slack coal. Never open or close any outlets of steam when your 
water is out of sight. 

Q. What precautions should you take to blow down a part of 
the water in your boiler while running with a good fire? A. 
Never leave the blow-off valve, and watch the water level. 

Q, How much water would you blow off at once while running? 
A. Never blow off more than one gauge of water at a time while 
running. 

Q. What precautions should the engineer take when necessary 
to stop with heavy fires? A. Close dampers, put on injector 
or pump, and if a bleeder is attached, use it. 

Q. What is an engineer's first duty on entering a boiler-room? 
A. To ascertain the true water level, and look at steam gauge. 

Q. When should a boiler be blown out? A. After it is cooled 
off — never while it is hot. 

Q. When laying up a boiler what should be done? A. Clean 
thoroughly inside and out ; remove all ' ' Rust ' ' and paint rust 
places with red lead ; examine all stays and braces to see if any 
are loose or badly worn. 

Q. Of what use is the indicator? A. The indicator is used to 
determine the power developed by an engine, to serve as a guide 
in setting valves and showing the action of steam in the cylinder. 

Q. How would you increase the power of an engine? A. To 
increase the power of an engine, increase the speed, or get higher 
pressure of steam ; or use less expansion. 

Q. How do you find the horse-power of an engine? 
_area of piston X M.E.P. X piston speed. 
33,000. 

Q. Which has the most friction, a perfectly fitted, or an im- 
perfectly fitted valve or bearing? A. An imperfect one. 



650 ' HANDBOOK ON ENGINEERING. 

Q. How hot can you get water under atmospheric pressure with 
exhaust steam ? A. 212°. 

Q. Does pressure have any influence on the boiling point? A. 
Yes. 

Q. Which do you think is the best economy, to run with your 
throttle wide open or partly shut ? A. Always have the throttle 
wide open on a governor engine. 

Q. At what temperature has iron the greatest tensile strength? 
A. About 600°, 

Q. About how many pounds of water are required to yield one 
horse-power with our best engines? A. From 15 to 30. 

Q. What is meant by atmospheric pressure? A. The weight 
of the atmosphere. 

Q. What is the weight of atmosphere at sea level? A. 14.7 
pounds. 

Q. What is the coal consumption per hour per indicated horse- 
power? A. Varies from 1| to 7 lbs. 

Q. What is the consumption of coal per hour on a square foot 
of grate surface? A. From 10 to 12 lbs. 

Q. What is the water consumption in pounds per hour per 
indicated horse-power? A. From 15 to 45 lbs. 

Q. How many pounds of water can be evaporated with one 
pound of best soft coal? A. From 7 to 10 lbs. 

Q. How much steam will one cubic inch of water evaporate 
under atmospheric pressure? A. One cubic foot of steam 
( approximately) . 

Q. What is the weight of a cubic foot of fresh water? A. 
62.425 lbs. 

Q. What is the weight of a cubic foot of wrought iron? A. 
480 lbs. 

Q. What is the last thing to do at night before leaving the 
plant? A. Look around for greasy waste, hot coals, matches, oi 
anything which could fire the building. 



HANDBOOK ON ENGINEERING. 651 

Q. What is the weight of a square foot of one-half inch boiler 
plate? A. 20 lbs. 

Q. How much wood equals one ton of soft coal for steam pur- 
poses? A. About 4,000 lbs. of wood. 

Q. What is the source of all power in the steam engine? A. 
The heat stored up in the coal. 

Q. How is the heat liberated from the coal ? A. By burning 
it — that is, by combustion. 

Q. Of what does coal consist? A. Carbon, hydrogen, nitro- 
gen, sulphur, oxygen and ash. 

Q. What are the relative proportions of these that enter into 
coal? A. There are different proportions in different specimens 
of coal, but the following shows the average per cent : Carbon, 
80 ; hydrogen, 5 ; nitrogen, 1 ; sulphur, 2 ; oxygen, 7 ; ash, 5. 

Q. What must be mixed with coal before it will burn? A. 
Air. 

Q. Of what is air composed? A. It is composed of nitrogen 
and oxygen in the proportion of 77 per cent nitrogen to 23 of 
oxygen. 

Q. What parts of the air mix with what parts of coal? A. 
The oxygen of the air mixes with the carbon and hydrogen of the 
<?oal. 

Q. How much air must mix with coal? A. 300 cubic feet of 
air for every pound of coal. 

Q. How many pounds of air are required to burn one pound of 
carbon? A. From 20 to 24, generally taken at 24. 

Q. How many pounds of air to burn one pound of hydrogen? 
A. Thirty- six. 

Q. Is hydrogen hotter than carbon ? A. Yes, 41 times hotter. 

Q. What part of the coal gives out the most heat? A. The 
hydrogen does part for part, but as there is so much more of 
carbon than hydrogen in the coal, we get the greatest amount of 
heat from the carbon. 



652 HANDBOOK ON ENGINEERING. 

Q. In how many different ways is heat transmitted? A, 
Three, by radiation, by conduction and convection. 

Q. If the fire consisted of glowing fuel, show how the heat 
enters the water and forms steam? A. The heat from the glow- 
ing fuel passes by radiation through the air space above the fuel 
to the furnace crown ; there it passes through the iron of the 
crown by conduction ; there, it warms the water resting on the 
crown, which then rises and parts with its heat to the colder water 
by conduction till the whole mass of water is heated ; then the 
heated water rises to the surface and parts with its steam, so a 
constant circulation is maintained by convection, 

Q. Of what does water consist? A. Oxygen and hydrogen. 

Q. In what proportion? A. Eight of oxygen to one of 
hydrogen, by weight. 

Q. What are the different kinds of heat? A. Latent heat, 
sensible heat and sometimes, total heat. 

Q. What is meant by latent heat? A. Heat that does not 
affect the thermometer and which expends itself in changing the 
nature of a body, such as turning ice into water or water into steam. 

Q. Under what circumstances do bodies get latent heat? A. 
When they are passing from a solid state to a liquid state, or from 
a liquid to a gaseous state. 

Q. How can latent heat be recovered? A. By bringing the 
body back from a state of gas to a liquid, or from that of a liquid 
to that of a solid. 

Q. What is meant b} r a thermal unit? A. The heat necessary 
to raise one pound of water, at any temperature — one degree 
Fah. 

Q. If the power is in coal, why should we use steam? A. Be- 
cause, steam has some properties which make it an invaluable 
agent for applying the energy of the heat to the engine. 

Q. What is steam? A. It is an invisible elastic gas generated 
from water by the application of heat. 

Q. What are the properties which make it so valuable to us ? 



HANDBOOK ON ENGINEERING. 653 

A.. 1. The ease with which we can condense it. 2. Its great 
expansive power. 3. The small space it occupies when con- 
densed. 

Q. Why do you condense the steam? A. To form a vacuum 
and so destroy the back pressure that would otherwise be on the 
piston, and thus get more useful work out of the steam. 

Q. What is vacuum? A. A space void of all matter. 

Q. How do you maintain a vacuum? A. By the steam used 
being constantly condensed by the cold water or cold tubes, and 
the air pump constantly clearing the condenser out. 

Q. Why does condensing the used steam form a vacuum? A. 
Because a cubic foot of steam at atmospheric pressure shrinks 
into about a cubic inch of water. 

Q. What do you understand by the term horse-power ? A. A 
horse-power is equivalent to raising 33,000 lbs. one foot per min- 
ute, or 550 lbs. raised one foot per second. 

Q. What do you understand by lead on an engine's valve? A. 
Lead on a valve is the admission of steam into the cylinder be- 
fore the piston starts its stroke. 

Q. What is the clearance of a cylinder as the term is applied 
at the present time? A. Clearance is the space between the 
cylinder head and the piston head, with ports included. 

Q. What are considered the greatest improvements on the 
stationary engine in the last forty years? A, The governor, the 
Corliss valve gear, and the triple compound expansion. 

Q. What is meant by triple expansion engine? A. A triple 
expansion engine has three cylinders, using the steam expansively 
in each one. 

Q. Is there any danger of a well-fitted and tightly -keyed fly- 
wheel coming loose? A. Yes ; water in the cylinder by produc- 
ing a heavy jar would tend to loosen a fly-wheel and frequently 
reversing an engine under a load and high speed, would tend to 
produce the same effect. 



654 HANDBOOK ON ENGINEERING. 

Q. What is a condenser as applied to an engine? A. The con- 
denser is a part of the low-pressure eDgine, and is a receptacle 
into which the exhaust enters and is there condensed. 

Q. What are the principles which distinguish a high-pressure 
from a low-pressure engine? A. Where no condenser is used and 
the exhaust steam is open to the atmosphere. 

Q. About how much gain is there by using the condenser? A. 
17 to 25 per cent, where cost of water is not figured. 

Q. What do you understand by the use of steam expansively? 
A. Where steam admitted at a certain pressure is cut off and 
allowed to expand to a lower pressure. 

Q. How many inches of vacuum give the best results in a con- 
densing engine? A. Usually considered 25". 

Q. What is meant by a horizontal tandem engine? A. One 
cylinder being behind the other, with two pistons on same rod. 

Q. What is a Corliss valve gear ? A. (Describe the half moon, 
or crab-claw gear, or oval-arm gear with dash pots.) 

Q. From what cause do belts have the power to drive shafting? 
A. By friction or cohesion. 

Q. What do you understand by lap? A. Outside lap is that 
portion of valve which extends beyond the ports when valve is 
placed on ' the center of travel ; and inside lap is that portion of 
valves which projects over the ports on the inside or towards the 
middle of valve. 

Q. What is the use of inside lap? A. To give the engine 
compression. 

Q. Where is the dead center of an engine? A. The point 
where the crank and the piston rod are in the same right line. 

Q. In what position would you place an engine to take up any 
lost motion of the reciprocating parts ? A. Place the engine in 
the position where the least wear takes place on the journals. 
That is, in taking up the wear of crank-pin brasses, place the 
engine on either dead center, as when running, there is little wear 



HANDBOOK ON ENGINEERING. 655 

upon the crank-pin at these points. If taking up the cross-head 
pin brasses — without disconnecting and swinging the rod — 
place the engine at half stroke, which is the extreme point of 
swing of the rod, there being the least wear on the brasses and 
cross-head pin in this position. 

Q. What benefits are derived from using fly-wheels on steam 
engines ? A. The energy developed in the cylinder while the steam 
is doing its work, is stored up in the fly-wheel, and given out by 
it while there is no work being done in the cylinder — that is, 
when the engine is passing the dead centers. This tends to keep 
the speed of the engine shaft steady. 

Q. Name several kinds of reducing motions, as used in indi- 
cator practice? A. The pantograph, the pendulum, the brumbo 
pulley, the reducing wheel. 

Q. How can an engineer tell from an indicator diagram whether 
the piston or valves are leaking? A. Leaky steam valves will 
cause the expansion curve to become convex ; that is, it will not 
follow hyperbolic expansion, and will also show increased back 
pressure. But if the exhaust valves leak also, one may offset the 
other, and the indicator diagram would show no leak. A leaky 
piston can be detected by a rapid falling in the pressure on the 
expansion curve immediately after the point of cut-off. It will 
also show increased back pressure. A falling in pressure in the 
upper portion of the compression curve shows a leak in the exhaust 
valve. 

Q. What would be the best method of treating a badly scaled 
boiler, that was to be cleaned by a liberal use of compound? A. 
First, open the boiler up and note where the loose scale, if any, 
has lodged. Wash out thoroughly and put in the required 
amount of compound. While the boiler is in service, open the 
blow-off valve for a few seconds, two or three times a day, to be 
assured that it does not become stopped up with scale. After 
running the boiler for a week, shut it down, and when the 



656 HANDBOOK ON ENGINEERING. 

pressure is down and the boiler cooled off, run the water out and 
take off the hand-hole plates. Note what effect the compound 
has had on the scale, and where the disengaged scale has lodged. 
Wash out thoroughly and use judgment as to whether it is advis- 
able to use a less or greater quantity of compound, or to add 
a small quantity daily. Continue the washing out at short 
intervals, as many boilers have been burned by large quan- 
tities of scale dropping on the fire sheets and not being 
removed. 

Q. What is an engineer's first duty upon taking charge of a 
steam plant? A. The first duty of an engineer assuming charge 
of a steam plant is to familiarize himself with his surroundings, 
ascertain the duty required of each and every piece of machinery 
contained therein, and in just what condition each one is. 
Let us discuss it at length, assuming that when just engaged he 
is informed as to the nature of the work required of the plant 
in question, namely: Whether it is a heating plant, electric 
lighting, hydraulic or electric elevator, power station, or any 
other kind of the various steam plants in existence. Of course, 
a great deal depends upon the size and kind of plant under con- 
sideration and. the number of men employed, hours in operation, 
and some other things in general which most engineers know of. 
He should first see just what his plant contains " from cellar 
to garret," so to speak ; whether all that is contained has to run 
continually, or almost so, and what can be depended on in case 
anything should suddenly become deranged or give out entirely. 
Next, he should ascertain the general condition of everything, 
going over each portion in turn, as time and opportunity permit, 
and conclude from what he has seen how much longer it may 
be run safely and economically. It will be remembered that a 
piece of machinery may be run safely and yet not with economy. 
So, if he should wait for the safety limit to be reached, 
without taking other things into consideration, he might wait 



HANDBOOK ON ENGINEERING. 657 

a long time and in so doing waste many dollars of his 
employer's money before it was thought necessary to reno- 
vate, repair or renew. In going over everything, examining 
each part critically, it would be well to make copious notes, and, 
I might add, sketches, to which the engineer can again refer. 
It sometimes happens that engineers, in making an examination 
of machinery, do not take dimensions or make sketches of certain 
parts which have to be repaired, or perhaps renewed, thinking 
that the next time the apparatus is looked at will do for that. 
Now, it sometimes happens that the " next time " is the time 
when some accident occurs, rinding you unprepared, causing con- 
fusion, in the midst of which the making of sketches and taking 
of dimensions cannot be thought of. All such should be done at 
the first opportunity, and spare parts of the different machinery 
should be kept on hand, especially in the case of a plant which 
has only the machinery which is constantly in use. Another point 
of importance to which an engineer should give attention, is to 
ascertain the quantity and kind of supplies which are on hand, 
that he may know when to make requisition for more, and so not 
run short, as he otherwise might do. It is also important to see 
what tools the plant contains and upon what you can depend in 
case of the break-down of any part of the machinery. Of course 
all the above cannot be done in one day, but no time should be 
lost in doing all these things as early as possible, for the sooner 
you get all the particulars and details of your plant at your 
"fingers' ends," the lighter will be your own labors, and the 
more free will your mind be to think and act intelligently for the 
emergencies of the future. Therefore, by performing this first 
duty as early and thoroughly as possible, the succeeding ones will 
be comparatively easy to handle and perform, for the reason that 
you will be prepared for them. 

Q. Define and explain the difference between sensible and 
latent heat? A. The difference between sensible and latent heat 

42 



658 HANDBOOK ON ENGINEERING. 

is explained thus : Sensible heat may be measured with a ther- 
mometer, that is, it affects the mercury in a thermometer, caus- 
ing it to rise in the stem so that the degree of heat may be 
measured on the graduated scale affixed. Latent heat does not 
affect the thermometer. Bodies get latent heat when they are 
passing from a solid state to a liquid state, and also when passing 
from a liquid to a gaseous state ; and moreover, this latent heat 
can be recovered by bringing a body back from a gaseous to a 
liquid state, and from liquid to solid. Water is most com- 
monly seen under the three forms of matter just mentioned, 
namely, solid, ice ; liquid, water ; gaseous, steam. The following 
method has been used to explain how latent heat exists : 
A quantity of powdered ice is placed in a vessel and brought 
into a very warm room. As long as it remains as ice, it may be 
any degree of heat below 32° Fahr., but the instant it begins to 
melt, owing to the heat of the room, a thermometer placed in it 
will record 32° Fahr. The thermometer will continue at 32° as long- 
as there is any ice in the vessel, but just as soon as the last piece of 
ice has melted it will begin to rise, and continue to do so until the 
water boils, when it will stand at 212° ; but although the water 
goes on receiving heat after this, the instrument will stand at 212° 
until all the water has boiled away. Now, a great amount of heat 
must have entered the water since the ice began to melt, but it has 
no effect on the thermometer, which continues at 32°, as noted 
above ; the heat that has so entered is called ' ' the latent heat of 
water." The heat that has entered the water from boiling 
till it all becomes steam is called the "latent heat of steam." 
The latent heat of water has been found to be 143° Fahr. 
and the latent heat of steam, at the pressure of the atmosphere, 
is 966°. This is the way the above was determined: A 
quantity of water at a temperature of 32° Fahr. is made to 
boil, and the time taken to do so noted ; in this case, it took one 
hour. The water must be kept boiling until it has all evaporated, 



HANDBOOK ON ENGINEERING. 659 

and the time noted from boiling till evaporation, which in this 
case will be 5-J hours. Therefore, 

Temperature of boiling point, ......... 212° 

Temperature of water at first, 32° 

Heat that has entered the water in one hour, . 180° 

Number of hours boiling, . . . . . . . . --. . 5| 

900 
60 

Heat that has entered during the 5-J hours, ....... 960° 

From this we see that the heat necessary to form steam, instead 
of being only 212°, must be 966° + 212° — 1178°, or 5* times as 
great. Therefore, if it were not for latent heat, we would require 
to burn 5J times the amount of coal that we now do to generate 
steam. The sensible and latent heats alter with the pressure, but 
as the sensible increases the latent decreases, and, roughly 
speaking, the total heat, or the sum of the two, is the same. In 
connection with the foregoing questions, I would recommend the 
reader to spend a little time in looking over the " steam tables," 
and make comparisons between the different quantities noted 
therein. By so doing he will get an exact knowledge of the prop- 
erties of saturated steam. 

Q. Explain the term " clearance," as used in connection with 
an engine cylinder ? A. There are two kinds of clearance, cylinder 
clearance and piston clearance . Cylinder clearance means the space 
or volume which exists between the piston and the valve, when 
the piston is exactly at the beginning of the stroke and the crank 
is on the dead center. This volume can be found by taking care- 
ful and exact measurements and making calculations from them, 
but a more correct way is to fill the space with water, noting the 
quantity used, and so make calculations to find the cubic con- 



660 HANDBOOK ON ENGINEERING. 

tents. The cubic contents of the clearance space is a certain per- 
centage of the total volume of the cylinder itself and such clear- 
ance is expressed as so much per cent. This clearance causes a 
small loss of steam each stroke, owing to the difference between 
the initial and compressive pressure. Piston clearance is the 
space between the piston and cylinder head when the crank is on 
the dead center. This clearance is necessary to prevent the 
cylinder head being knocked out, in case of an unusual quantity 
of water gaining entrance to the cylinder while the engine is 
running at its usual speed ; and also to admit of the crank-pin 
and wrist-pin brasses being keyed up at certain intervals. The 
way to find the piston clearance of an engine is as follows : 
First, disconnect the wrist-pin end of the connecting rod from 
the cross-head, and with a bar push back the cross-head until 
the piston strikes the cylinder head ; then make a mark with 
a scriber or sharp chisel, on both the sides of the cross-head and 
on the guide in which the cross-head runs ; these marks must be 
exactly in line with each other while the piston is in the above 
stated position. Next, move the piston to the other end of the 
cylinder till it strikes the head, and make a mark on the guide 
similar to that on the other end, using the same mark which was 
made on the cross-head. The new mark must also be in line with 
this, as at the first mentioned end. You now have a mark at 
each end of the guide, which represents the place at which the 
piston strikes the cylinder head, when they alternately coincide 
with the mark on the cross-head itself. Now, connect the rod 
to the cross-head again and place the engine or crank on the center. 
Next, produce or extend the mark on the cross-head to the guide, 
this time using a pencil instead of a chisel and scriber. The 
distance between the new pencil mark and the first mark made 
on the guide is the amount of piston clearance which exists at 
that end of the cylinder. Repeat the operation on the other end 
and you will obtain the clearance existing there. If these clear- 



HANDBOOK ON ENGINEERING. 661 

ances are not equal, as indicated by the marks, make them so 
by the means provided for in the design of the piston rod and 
crosshead. After the clearance has been equalized, the pencil 
marks may be obliterated and marks similar to the first ones may 
be cut in, thus leaving a permanent mark which can be seen while 
the engine is running, and from which can be determined whether 
the clearance is lessening, and at which end. 

Q. What is the pressure of the atmosphere at the sea level, and 
how determined? A. The pressure of the atmosphere is generally 
spoken of as 15 lbs. per square inch, but as the pressure of the 
atmosphere is constantly varying at any one spot, corrections 
have to be made according to the reading of a barometer. 
Generally speaking, 15 is as nearly correct as engineers require 
it. The pressure of the atmosphere can be ascertained by the 
following experiment: Take a glass tube about 33 inches long, 
having a bore equal to a square inch in section. Let one end of 
the tube be closed in or capped, so that it can contain a fluid. 
Then fill it with pure mercury, carefully expelling any air bub- 
bles. When it is full, cover the open end of the tube with a piece 
of glass and invert the whole tube. Place the open end into a 
cup of mercury, the surface of which is subject to the pressure of 
the air, and then withdraw the piece of glass. The mercury in 
the tube will drop about three inches and then stop. When it 
has ceased to fall, again cover the end of the tube with the glass. 
Lift the tube out of the cup and remove the glass so that the 
mercury may run out into a scale-pan provided for that purpose. 
Upon actually weighing the mercury lately contained in the tube, 
it will be found to weigh 14.7 lbs. The mercury will stop falling 
in the tube at 30 inches, or at the sea level. Hence, we know 
that the atmosphere balances, or exerts a pressure of 14.7 lbs. 
per square inch at the sea level. 

Q. Upon what does the efficiency of a surface condenser de- 
pend? A. The efficiency of a surface condenser depends upon: 



662 HANDBOOK ON ENGINEERING. 

1st, the proper amount of cooling surface ; 2d, the rapidity with 
which the water is made to circulate through the tubes ; 3d, the 
water being made to flow in an opposite direction to the steam. 
The temperature of the circulating water also has a bearing on 
the question, as it is obvious that the colder the water the more 
effective it will be in condensing the steam. 

Q. A feed pump has a steam cylinder of 6 inches in diameter, 
and water cylinder of 4 inches diameter ; assuming the steam 
pressure carried to be 80 lbs. per square inch throughout the 
stroke, what will be the balancing pressure per square inch 
against the water piston, friction being entirely neglected, and 
gauge pressure being used? A. In this question, we first find 
the area, the number of square inches contained in the steam 
piston. Thus : The diameter = 6 in. and 6 2 x .7854 = the area. 
Worked out it appears thus : 6 2 means that 6 is to be 
squared, or multiplied by itself, or 6 x 6 — 36 square inches, 
and 36 square inches multiplied by the constant .7854 = 
28.27 square inches area contained in the steam piston. 
Since the pressure is stated to be 80 lbs. per square inch, then 
28.27 x 80 = total pressure on the piston in pounds, or 2261.60 
lbs. Now, we will find the area of the water piston, which is 4 
inches in diameter, 4 2 x .7854 = 12.5664 square inches contained 
in the water piston. Therefore, the water piston, with an area 
of 12.56 sq. in., has to have a resistance against which it will act 
of 2261.60 lbs., in order to balance the pressure against the 
steam piston. Hence, the pressure per square inch can be found 
by dividing 2261.60, or 2261.60 divided by 12.56 = 180 lbs. per 
square inch, the balancing pressure on the 4-inch water piston. 

Q. State what you consider a good standard of strength for 
steel boiler plate? A. The American Boiler Makers' standard, 
as used, is as follows: Tensile strength, from 55,000 to 60,000 
lbs. per square inch section ; elongation in 8 inches, 20 per cent 
for plates | inch thick and under ; 22 per cent for plates f to j- 



HANDBOOK ON ENGINEERING. 663 

inches ; 25 per cent for plates J inch and under ; the specimen 
test piece must bend back on itself when cold, without showing 
signs of fracture ; for plates over i inch thick, specimens must 
withstand bending 180° (or half way) round a mandrel 1J times 
the thickness of the plate. The chemical requirements are as 
follows: Phosphorus, not over .04 per cent; sulphur, not over 
.03 per cent. 

Q. What is meant by the heating surface of a boiler? A. The 
heating surface of a boiler is that surface of plates or tubes on 
one side of which is water, and on the other hot gases. It has 
been decided that the surface next the water shall be reckoned, 
the value to be given in square feet. In a fire tube, or tubular 
boiler, it will include the under side of the shell from fire-line to 
fire-line (usually about one-half of it), the tubes and such part of 
the back-tube sheet as is below the back arch and not taken up 
by the tube ends,. For a water-tube boiler, the heating sur- 
face will include the tubes, such part of the headers as are 
in contact with the hot gases, and the lower part (about one- 
half) of the steam drum. In calculating the heating surface, 
none should be taken which has steam on one side and hot gases 
on the other, as such parts tend to superheat the steam, and are 
known as superheating surfaces. 

Q. What is a boiler horse-power? A. A boiler horse-power 
has been recently defined as the evaporation of 34i pounds of 
water per hour from a feed water temperature of 212° Fahr. 
into steam at a temperature of 212° Fahr., and at a pressure of 
one atmosphere. Under these conditions each pound of water 
evaporated will take up 966 heat units, and the 34i lbs. will take 
34i x966 = 33,327 heat units per hour. Hence, to find the 
horse-power of a boiler, it is necessary to find the heat units 
delivered per hour to the water and divide that number by 33,327. 

Q. What will be the heatiug surface of a fire-tube boiler 6 
feet in diameter, having 150 tubes 3 inches in diameter and 15 



664 HANDBOOK ON ENGINEERING. 

feet long? A. Each tube will have a heating surface equal to its 
outside area, since the water is on the outside of the tubes. The 
area of a cylinder 3 in. in diameter and 15 ft. long will be the 
circumference times the length ; 3 in. ==i ft. and the circumfer- 
ence = 3.1416 xi == .7854 ft.; this, times the length 15 ft. 
= 11.78 sq. ft. for one tube ; for 150 tubes, it will be 150 times 
that = 1767 sq. ft. The lower half of the shell is usually con- 
sidered as heating surface. The circumference of a circle 6 ft. in 
diameter is 6x3.1416 =18.85 ft. and the area of the shell — 
18.85x15=282.75 sq. ft. Half this will be 141.37 sq. ft. 
For the back end or tube plate, the total area will be the diameter 
squared times .7854 = 6 2 x .7854 = 28.27 sq. ft. ; f of this will 
be below the arch, and | of 28.27 = 18.85 sq. ft. From this 
must be subtracted the area of the ends of the tubes. The end 
area of one tube is (J) 2 x .7854 = .049 sq. ft., and for 150 
tubes it is 150 times that, or 7.35 sq. ft. The heating surface of 
the tube plate will then be 18.85 minus 7.35 = 11.5 sq. ft. The 
front tube plate is not considered, because the gases are cooled 
too much to be effective by the time they have passed through 
the tubes. The total heating surface is 1767 + 141.37+ 11.5 
= 1919.87 sq. ft. 

Q. On what does the efficiency of a boiler depend? A. The 
efficiency of any piece of machinery is the ratio of the energy made 
useful to that furnished. The object of the boiler is to make steam ; 
hence, the enegy used is that which has gone into the steam. The 
proportion of the heat generated in the furnace which is transferred 
to the steam, will depend on the thickness of the plates of the 
boiler, on their condition as to cleanliness, on the amount of time 
during which the gases are in contact with the plates in their 
passage from furnace to chimney, on the completeness with which 
all parts of the gases are brought in contact with the plates, and on 
the temperature of the hot gases. Evidently, heat will pass through 
a thin plate more readily than through a thick one, and more 



HANDBOOK ON ENGINEERING. 665 

readily through a clean plate than through one on which a non- 
conducting coating of soot or scale has formed ; the more time 
available for the transfer of heat, the greater will be the amount 
transferred ; the more complete the contact between plates and 
gases, the more opportunity will there be for the transfer of heat, 
and the higher the temperature of the gases, the more rapidly 
will the heat be transferred. To have a boiler efficient, it is 
necessary to have plenty of heating surface, so that the hot gases 
will have time for contact, to keep the plates clean, to have good 
circulation of the gases, and to keep their temperature high by 
preventing radiation and allowing as little air to enter the furnace 
as is needed for good combustion. The efficiency of the furnace, 
that is, the ratio of the heat generated in the furnace to that con- 
tained in the coal, is a separate matter, though often the two are 
lumped together. It depends on the adaptation of the furnace to 
the kind and size of coal used, on the size of the combustion 
chamber and on the proper firing of the coal. 

Q. On what its satisfactory working? A. In order to 
work satisfactorily, a boiler must not only be efficient, but must 
make steam rapidly, must make dry steam, must be easily fired 
and cleaned, and must be capable of standing a considerable 
amount of forcing without serious priming. To get rapid steam 
making, it is necessary to have good circulation of the water in the 
boiler ; to get dry steam, plenty of steam space is needed, so that 
the steam may circulate slowly and allow the water to drop out of 
it; easy firing means a low fire door of good size, and a rather 
short grate; easy cleaning means accessible parts, good sized 
man-holes, good sized and well placed hand-holes, a large blow- 
off and a short boiler ; the prevention of priming when carrying 
an overload is a difficult matter ; the tendency to such an occur- 
rence depends largely on the feed-water used ; plenty of steam 
space and good circulation are helpful, but some waters will foam 
in spite of all precautions. 



Q6Q 



HANDBOOK ON ENGINEERING. 



Q. Suppose a slide valve cutting off at J stroke, and a | cut- 
off is desired, how would you proceed? A. Put on a new valve 
with more outside lap. This would require a greater travel of the 
valve, consequently, I would increase the throw of the eccentric, 
also. 

Q. Which requires the greater outside lap, cutting off at T 9 F of 
the stroke, or cutting off at J? A. Cutting off at T 9 g. The 
earlier the cut-off, the greater should be the outside lap. 

Q. Are all plain slide valves made alike, as regards the exhaust 
cavity of the. valve ? A. No ; sometimes they are made ' ' line and 
line " inside, that is, the width of the exhaust cavity is equal to 
the distance between the inner edges of the two steam ports ; and 
again, the width of the exhaust cavity is made greater or less than 
this distance, according as an earlier or later release is desired. 

Q. What is the effect of giving inside lap to a slide valve? A. 
It delays the release and increases the compression. 

Q. What is the effect of giving inside lead to a slide valve? 
A. It gives an early release and decreases the compression. 

Q. Suppose a simple slide valve engine with a fly-ball governor, 
and the governor belt should break or slip off, what would 
happen? A. If it were a plain governor the engine would race; 
but if a governor with an automatic stop, the engine would slow 
down and stop. 

Q. What two forces are opposed to each other in a case of fly- 
ball governor? A. Centrifugal force, tending to throw the balls 
away from the governor staff, and the force of gravity, tending to 
draw the balls to the staff. 

Q. What other name is given to a fly-ball governor? A. It is 
also called a throttling governor, because the steam in passing 
through the governor valve is throttled, choked, or wire- 
drawn. 

Q. Are all fly-ball governors throttling governors? A. No; 
the governor of a Porter-Allen engine and those of all Corliss 



HANDBOOK ON ENGINEERING. 667 

engines, while of the fly-ball type, are not throttling governors, 
because the steam does not pass through them. 

Q. If the governor shaft of a fly-ball governor on a plain slide- 
valve engine should break, could the engine be run? A. Yes; 
by regulating the speed of the engine by hand at the throttle- 
valve. 

Q. Describe an automatic cut-off engine? A. In this class of 
engines, as the load on the engine becomes greater or less, the 
steam entering the cylinder is cut off later or earlier, and it is 
done through a fly-ball governor in the case of a Corliss engine, 
or through a shaft-governor or regulator in the case of a high- 
speed engine. 

Q. In an automatic cut-off high-speed engine with shaft-gov- 
ernor, is the eccentric fastened to the shaft? A. It is not. It 
is so arranged as to move freely across the shaft, in order to per- 
mit the center of the eccentric to approach or to recede from the 
center of the shaft, according as the load on the engine decreases 
or is increased. And herein lies the chief difference between a 
plain slide-valve and an automatic cut-off slide-valve engine. 

Q. If the connecting rod of an engine had box liners at both 
ends and in taking it down the liners were all mixed up, how 
could the length of the rod from center to center of boxes be 
found? A. Put the cross-head in the middle of its stroke — 
after finding the piston striking points — and then measure from 
the center of the cross-head wrist to the center of the main shaft. 
If the piston clearance at both ends of the cylinder is known, the 
piston may be pushed to the crank end of the cylinder until it 
touches the head, and the distance from the center of the cross- 
head wrist to the center of the main shaft found, to which should 
be added the length or throw of the crank, and also the piston 
clearance at the crank end of the cylinder. 

Q. But suppose it were more convenient to push the piston to 
the head end of the cylinder, what then? A. Find the distance 



668 HANDBOOK ON ENGINEERING. 

from the center of cross-head wrist to center of main shaft and 
deduct the throw of the crank, and also the clearance. 

Q. How is the length of the valve stem and of the eccentric 
rod found for a plain slide valve engine having a rock shaft? A. 
If the motion of the slide valve is parallel with the motion of the 
piston, the length of the valve stem may be found by measuring 
in a horizontal line from the center of the valve seat to the center 
of the rock shaft ; and for the eccentric rod by measuring from 
the center of the rock shaft, horizontally, to the center of the 
main shaft, which would include one-half the yoke. 

Q. What is a direct, and also an indirect valve motion? A. 
When there is no rock shaft between the eccentric and the valve 
to compound the motion, it is called " direct," and when a rock 
shaft intervenes, it is called an " indirect " valve motion. 

Q. Is the valve motion of a Corliss engine direct or indirect? 
A. It is direct. 

Q. How so ; it has a rock shaft between the eccentric and 
the wrist plate? A. Even so, it is a direct valve motion ; because 
all connections to the rock-shaft arm are above the center of the 
shaft, consequently, the motion is simple and not compound. 

Q. When is an engine said to " run under," and when to " run 
over? " A. When the crank pin is above the center of the main 
shaft and the pin moves towards the cylinder, the engine is said 
to " run under ; " and when it moves away from the cylinder, the 
engine is said to " run over." 

Q. What is meant by lead of valve, and what is it for? A. 
Lead is the amount that the port is open to steam when the crank 
is on its center. It is given in order to allow the full pressure of 
steam to come on the piston at the beginning of the stroke, and 
to provide a cushion for the piston. 

Q. Could not cushion for the piston be obtained in some other 
manner? A. Yes, by producing compression by an early closing 
of the exhaust. 



HANDBOOK ON ENGINEERING. 6(39 

Q. Suppose a slide valve had J" lap and no lead, and it was 
desired to give it -j--' l ea d? how should it be done? A. By mov- 
ing the eccentric. 

Q. Why could it not be done by altering the length of the 
eccentric rod ? A. Because the eccentric rod does not establish 
the amount of lead ; it simply equalizes the lead given by 
moving eccentric. 

Q. How would you test the piston of a steam engine to see 
whether it was steam-tight or not? A. Put the crank on the 
outboard center ; remove the cylinder head on the head end ; 
block the cross-head and admit steam to the crank-end of 
cylinder and note the effect. The fly-wheel, or the cross-head 
may be securely blocked and the piston tested in this manner at 
different points in the stroke. 

Q. Why are two eccentrics and two wrist plates put on some Corliss 
engines? A. One eccentric is for the induction valves to lengthen 
the range of the cut-off ; the other for the exhaust valves to admit 
of early release, without excessive compression. With a Corliss 
engine having but one eccentric, the limit of cut-off is at less than 
one-half stroke, but with two eccentrics the cut-off may be still 
later in the stroke, and still release the steam at the proper time. 

Q. What is meant by a " blocked up " governor on a Corliss 
engine? A. When the safety stop is " in " the governor is said 
to be blocked up. 

Q. With a blocked up governor, suppose the main driving belt 
should break, what would be the result? A. The engine would 
race and would, perhaps, be wrecked. 

Q. What is meant by the fire line of a horizontal cylindrical 
boiler? A. It is the height to which the shell is exposed to the 
action of the flames. 

Qi How high should the fire line be run? A. It may be run as 
high as the lower gauge cock water level, although it is frequently 
run no higher than the top row of flues. 



670 HANDBOOK ON ENGINEERING. 

Q. What causes a chimney or smoke-stack to draw ? A. The 
difference in the temperature of the air inside the chimney and 
that outside. The air inside expands and exerts less pressure 
than the outside air, which rushes in to equalize the pressure. 

Q. What does the amount of grate surface determine? A. It 
determines the amount of coal that can be burned per hour, and 
consequently, the amount of steam that can be generated. 

Q. What is the object in giving a slide valve outside lap? A. 
To save steam by cutting off the flow of steam into the cylinder 
before the piston reaches the end of its stroke. For example: 
With 24 in. stroke of piston and | cut-off, the flow of steam to 
the piston is cut off when the piston has moved 15 inches and it 
is driven the remaining 9 inches by the expansive force of the 
steam. 

Q. What amount of refrigerating water is required for a con- 
denser? A. For a surface condenser about 50 times, and for a 
jet condenser 30 times the amount of water evaporated in the 
boiler ; more or less than these quantities being required accord- 
ing to the temperature of the exhaust steam. 

Q. Suppose your condenser was out of order and undergoing 
repairs, could you run the engine? A. Yes; by attaching an 
exhaust pipe to the engine and exhausting into the atmosphere. 

Q. With a lever safety valve, should the end of the valve stem 
upon which the lever rests, be square or concave? A. Neither 
one; it should be pointed, so that the lever will always bear 
directly on a line with the center of the valve stem. 

Q. What is the proper proportion of a safety valve lever? A. 
About 7 to 1 ; that is, if the distance from the center of the 
valve to the fulcrum is 1 inch, the distance from the center of the 
valve to the end of the long arm of the lever should be about 7 
inches. 

Q. How should the grates be set in a boiler furnace? A. 
They should be set level, because this plan will enable the fire- 



HANDBOOK ON ENGINEERING. 



(571 



man to more easily carry a bed of fuel of uniform depth ; besides, 
it is less laborious to clean the fire than when the grates are lower 
at the bridge wall. 

Q. What is momentum? A. It is the product of the mass or 
bulk of a moving body, taken in pounds or tons, multiplied by the 
velocity of the moving mass, generally taken in feet per second. 

Q. Will an injector work at the same steam pressure when it 
lifts the water as when the water flows to it under pressure ? A. 
No ; when the water flows to an injector under pressure it will 
work down to the lowest steam pressures, but when lifting the 
water it requires a steam pressure of ten pounds or over to work 
the injector. 

Q. What is the greatest height to which an injector will lift 
water? A. That depends upon the starting steam pressure. 
There are injectors that will lift water two feet with 10 lbs. 
steam pressure, five feet with 30 lbs., and from 12 to 25 feet with 
60 lbs. and over. 

Q. If the pulley on the main shaft of an engine driving a fly- 
ball governor be reduced in diameter, what effect will it have on 
the speed of the engine? A. The speed of the engine will be 
increased. 

Q. Which is the greater, the bursting or the collapsing pressure 
of a boiler tube? A. A boiler tube will collapse under less pres- 
sure than would be required to burst it. 

Q. Should a horizontal externally fired boiler be set level or 
with a pitch? A. It is customary to set such a boiler one inch 
lower at the end to which the blow-off pipe is attached, in order 
to drain the boiler readily. 

Q. In a slide valve engine with a connecting rod, will the valve 
cut off the same at both ends of the stroke if it has equal lap and 
lead? A. No ; owing to the angularity of the connecting rod. 

Q. Is it proper to close the damper with a banked fire? A. 
The damper should never be closed tightly while there is fire. 



672 



HANDBOOK ON ENGINEERING. 



CHAPTER XXIII. 
INSTRUCTIONS FOR LINING UP EXTENSION TO LINE SHAFT. 

The erection of a line shaft, or an extension to one, is a 
job that should have the services of a competent millwright or 
machinist, as it is one calling for experience and considerable 
skill. 

I will, however, give you some pointers on how to proceed. A 
linen line or fine wire should be stretched beneath the shaft and 
parallel to it, and extending beyond the termination of the 
extension. 



Oa 9. 



^ 



To set the line parallel to the main line shaft, hang the plumb- 
bobs A A over the shaft, as shown-in the sketch, and then adjust 
the line until it just touches the lines supporting the bobs, with- 
out disturbing their position. If the plumb-bobs trouble you by 
swaying, set pails of water so that the bobs will be immersed ; 
this will stop the swaying without destroying their truth. The 
plumb-bobs may just as well be old nuts or similar pieces of iron, 



HANDBOOK ON ENGINEERING. 673 

as the regulation type, since the result will be exactly the same. 
After getting the line adjusted to the desired position, suspend 
the plumb-bobs A A along the direction of the extension, so that 
their supporting cords will just touch the line without disturbing it. 
The new section of the shaft is now brought in position sideways 
until it also touches the cords of the plumb-bobs ^1 A , which, of 
course, locates it parallel with the main shaft in a horizontal plane. 
To get it to the right height, enter the shaft coupling of the new 
part into coupling of the main shaft, and then adjust until the 
shaft shows level when tested with an accurate spirit level. A 
level suitable for this work should be of iron and planed on the 
under side with a V-groove, which will always locate it parallel 
with the shaft when testing it. Before leveling the new part of 
the shaft, it will be necessary to try the shaft already in position, 
as it may not be level. If found " out "it should be leveled, 
but sometimes this will not be possible or feasible, in which case 
it will be necessary to set the new part at the same inclination. 
To do this, test the main shaft and find how much it is out, and 
adjust the level by strips of paper until it shows " fair." The 
paper should be secured to the level by glue or other means and 
used on the new shaft in that condition, always keeping the level 
with the " packed " end pointing in the same direction. After 
getting the new part in position, it is well to test it before con- 
necting it to the main part ; that is, it should be turned by hand 
to determine if the frictional resistance is excessive or not. After 
connecting with the main part, it is not a bad idea to test it again 
by hand, if possible. With a long shaft it may be necessary to 
disconnect the further sections and remove the belts from the 
connected machines. In this way a fair idea of the frictional 
resistance may be obtained. As before stated, this work requires 
experience and skill, and should properly be clone by one thor- 
oughly competent for the work ; for, while his services may seem 
a trifle expensive, it will usually be found to pay better in the 

43 



674 HANDBOOK ON ENGINEERING. 

long run, as the frictional resistance of an improperly lined shaft 
will quickly consume coal enough to pay the difference. 

SIMPLICITY IN STEAM PIPING. 

In building steam power plants, and especially in arranging 
the piping connections for them, simplicity is a characteristic the 
value of which is often too little appreciated. It should be borne 
in mind that extra valves and duplicate piping mean a very 
considerable amount of capital lying at waste to meet a contin- 
gency which may, in all probability, never arise, not to speak of 
the care and attention required to keep piping and valves which 
are rarely used in shape for service. Another point which ought 
to be realized in the design of piping, is that every square foot of 
uncovered surface, as in flanges and the like, causes the loss of 
about one dollar per year in condensation of steam , and each square 
foot of uncovered surface represents the loss of nearly one-quarter 
of this amount. The principle of construction is to design the 
piping with the utmost simplicity possible ; without any double 
connections, put it up so that no accidents can happen to it. It 
is argued that this is impossible, but it is equally impossible to 
insure absolute immunity against " shut downs," of greater or 
less duration, by any amount of duplex connections, for even 
the blowing out of a single gasket can blow down a whole battery 
of boilers before a 12 -inch valve can be closed and another 
opened. With the more extensive introduction of high-pressure 
valves and fittings, it is possible, by proper design, to reduce 
the liability to accident very nearly to the point of absolute 
safety, and by the introduction of one or two extra valves, it is 
generally possible to divide the plant into sections, any one of 
which can, if occasion demands, be operated independently. No 
fixed rules can be laid down and the line between absolute sim- 
plicity and necessary complexity must be drawn separately for 
each plant with due regard to the work it has to perform , but it 



HANDBOOK ON ENGINEERING. 



675 



should be remembered that the more simple a plant can be made 
to accomplish the work with absolute reliability, the greater the 
achievement in economy of first cost, and in availability and 
economy of operation. 




Diagram Showing Screwed Valve ana Fittings 




jflaL - ■ ^ j2 ^ fcff liDj j B| . cfrg jTl 




"ceip — n§%^%^^-r~&- — tt~j 



, .. .,:... 



Diagram Showing Flanged Valve and Fittings 



CUTTING PIPE TO ORDER. 



In placing 1 orders for pipe, a diagram should be made, accord- 
ing to above cuts. Great care should be taken in making a 
diagram for large pipe ; all measurements should be from centers. 
When flanged fittings are used, state if desired drilled, and if 
with bolts and gaskets complete. Also state if you desire the 



676 



HANDBOOK ON ENGINEERING. 



fittings made up tight, and mark such pieces at point joint is 
desired, on diagram. 



FEED=WATER REQUIRED BY SHALL ENGINES. 



Pressure of Steam 

in Boiler, by 

Gauge. 


Pounds of Water 

per Effective 

Horse -power per 

Hour. 


Pressure of Steam 

in Boiler, by 

Gauge. 


Pounds of Wate 

per Effective 

Horse- power per 

Hour. 


10 






118 


60 






75 


15 






111 


70 






71 


20 






105 


80 






68 


25 






100 


90 






65 


30 






93 


100 






63 


40 






84 


120 






61 


50 






79 


160 






58 



HEATING FEED=WATER. 

Feed-water, as ^ comes from the wells or hydrants, has ordi- 
narily a temperature of from 35° in winter to from 60 to 70° in 
summer. Much fuel can be saved by heating this water by the 
exhaust steam, whose heat would otherwise be wasted. Until 
quite recently, only non-condensing engines utilized feed water 
heaters but lately they have been introduced with success between 
the cylinder and the air-pump in condensing engines. The 
saving in fuel due to heating feed-water is given on page 644. 



RATING BOILERS BY FEED=WATER. 

The rating of boilers has, since the Centennial Exposition in 
1876, been generally based on 30 pounds feed water per hour per 
horse-power. This is a fair average for good non-condensing engines 
working under about 70 to 100 ponnds pressure. But different 



HANDBOOK OX ENGINEERING. 



(377 



pressures and different rates of expansion change the require- 
ments for feed water. The following table gives Prof. R. H. 
Thurston's estimate of the steam consumption for the best classes 
of engines in common use when of moderate size and in good 
order : — 



WEIGHTS OF FEED WATER AND OF STEAM. 

NON CONDENSING ENGINES. — R. H. T. 



Steam Pressure. 


Lbs. per H. P. 


per Hour. — Ratio of Expansion. 


Atmos- 
phere. 


JLbs. per 
sq. iD. 


2 


3 


4 


5 


1 
7 10 


3 


45 


40 


39 


40 


40 


42 


45 


4 


60 


35 


34 


36 


36 


38 


40 


5 


75 


30 


28 


27 


26 


30 


32 


6 


90 


28 


27 


26 


25 


27 


29 


7 


105 


26 


25 


24 


23 


25 


27 


8 


120 


25 


24 


23 


22 


22 


21 


10 


150 


24 


23 


22 


21 


20 


20 



CONDENSING ENGINES. 



2 


30 


30 


28 


28 


30 


35 


40 


3 


45 


28 


27 


27 


26 


28 


32 


4 


60 


27 


26 


25 


24 


25 


27 


5 


75 


26 


25 


25 


23 


22 


24 


6 


90 


26 


24 


24 


22 


21 


20 


8 


120 


25 


23 


23 


22 


21 


2G 


10 


150 


25 


23 


22 


21 


20 


19 



Small engines having greater proportional losses in friction, in 
leaks, in radiation, etc., and besides receiving generally less care 



678 HANDBOOK ON ENGINEERING. 

in construction and running than larger ones, require more feed 
water (or steam) per hour, 

FEED-WATER HEATERS. 

Inattention to the temperature of feed water for boilers is en- 
tirely too common, as the saving in fuel that may be effected by 
thoroughly heating the feed water — by means of the exhaust 
steam in a properly constructed heater — would be immense, as 
may be»seen from the following facts : A pound of feed water en- 
tering a steam boiler at a temperature of 50° Fahr., and evapo- 
rating into steam of 60 lbs. pressure, requires as much heat as 
would raise 1157 lbs. of water 1 degree. A pound of feed water 
raised from 50° Fahr. to 220° Fahr. requires 987 thermal units 
of heat, which if absorbed from exhaust steam passing through a 
heater, would be a saving of 15 per cent in fuel. Feed water at a 
temperature of 200° Fahr., entering a boiler, as compared in point 
of economy, with feed water at 50°, would effect a saving of over 
13 per cent in fuel ; and with a well-constructed heater there ought 
to be no trouble in raising the feed water to a temperature of 212° 
Fahr. If we take the normal temperature of the feed water at 60°, 
the temperature of the heated water at 212° and the boiler pressure 
at 20 lbs., the total heat imparted to the steam in one case is 
1192.5° minus 60° = 1132.5°; and in the other case, 1192.5° 
minus 212° — 980.5°, the difference being 152°, or a saving of 
152/1132.5 = 13.4 per cent. Supposing the feed water to enter 
the boiler at a temperature of 32° Fahr., each pound of water will 
require about 1200 units of heat to convert it into steam, so that 
the boiler will evaporate between 6| and 7 \ lbs. of water per 
pound of coal. The amount of heat required to convert a pound 
of water into steam varies with the pressure, as will be seen by 
the following table : — 



HANDBOOK ON ENGINEERING. 



679 



TABLE SHOWING THE UNITS OF HEAT REQUIRED TO CONVERT ONE POUND 
OF WATER, AT THE TEMPERATURE OF 32° FAHR., INTO STEAM AT 
DIFFERENT PRESSURES. 



Pressure of 
Steam in lbs. per 
Sq. In. by Gauge. 



Units of Heat. 



Pressure of 
Steam in lbs. per 
Sq. In. by Gauge. 



Units of Heat. 



1 


1,148 


110 


1,187 


10 


1,155 


120 


1,189 


20 


1,161 


130 


1,190 


30 


1,165 


140 


1,192 


40 


1,169 


150 


1,193 


50 


1,173 


160 


1,195 


60 


1,176 


170 


1,196 


70 


1,178 


180 


1,198 


80 


1,181 


190 


1,199 


90 


1,183 


200 


1,200 


100 


1,185 







If the feed water has any other temperature the heat necessary 
to convert it into steam can easily be computed. Suppose, for 
instance, that its temperature is 65°, and that it is to be converted 
into steam having a pressure of 80 lbs. per square inch. The 
difference between 65 and 32 is 33 ; and subtracting this from 
1181 (the number of units of heat required for feed water hav- 
ing a temperature of 32°), the remainder, 1148, is the number of 
units for feed water with the given temperature. Yet it must be 
understood that any design of heater that offers such resistance 
to the free escape of the exhaust steam as to neutralize the gain 
that would otherwise be obtained from its use, ought to be 
avoided, as the loss occasioned by back pressure on the exhaust, 
in many instances, counteracts the advantages derived from the 
heating of the feed water. 



Feed-water heaters are a most important feature of a good 
steam plant. First, by utilizing the heat of the exhaust steam 



680 



HANDBOOK ON ENGINEERING. 



from the engine or waste gases in chimney, the feed water may be 
heated to about 210° Fahr., with ease, before entering boilers, 
by this means saving fuel and increasing capacity of boiler. 
Second. By heating the water, the boilers are protected from 
serious and unequal strain, as the difference of temperature be- 
tween incoming water and outgoing steam may be kept about 110 
(210° to 320°). Third. Every heater must necessarily be a 
water purifier, as the mud and lime are eliminated, to some degree 
at least, before the water reaches the boiler, by heat. 

TABLE. 

SHOWING GAIN IN USE OF FEED WATER HEATER. PERCENTAGE OF 
HEAT REQUIRED TO HEAT WATER FOR DIFFERENT FEDD AND BOIL1LN 
TEMPERATURES, AS COMPARED WITH A FEED AND BOILING TEM- 
PERATURE OF 212°. 



Boiling 


Initial Temperature of feed 


water. 






Point. 






































Fahr. 


32° 


50° 


68° 


86° 


104° 


122° 


140° 


158° 


176° 


194° 


212° 


212 


1.19 1.17 


1.15 


1.13 


1.11 


1.10 


1.08 


1.06 


1.04 


1.02 


1.00 


230 


1.20 


1.18 


1.16 


1.14 


1.12 


1.10 


1.08 


1.06 


1.04 


1.02 


1.01 


248 


1.20 


1.18 


1.16 


1.14 


1.13 


1.11 


1.09 


1.07 


1.05 


1.03 


1. 01 


266 


1.21 


1.19 


1.17 


1.15 


1.13 


1.11 


1.09 


1.07 


1.06 


1.04 


1.02 


284 


1.21 


1.20 


1.18 


1.16 


1.14 


1.12 


1.10 


1.08 


1.06 


1.04 


1.02 


302 


1.22 


1.20 


1.18 


1.16 


1.14 


1.12 


1.11 


1.09 


1.07 


1.05 


1.03 


320 


1.22 


1.21 


1.19 


1.17 


1.15 


1.13 


1.11 


1.09 


1.07 


1.05 


1.03 


338 


1.23 


1.21 


1.19 


1.17 


1.15 


1.14 


1.12 


1.10 


1.08 


1.06 


1.04 


356 


1.23 


1.22 


1.20 


1.18 


1.16 


1.14 


1.12 


1.10 


1.08 


1.06 


1.04 


374 


1.24 


1.22 


1.20 


1.18 


1.17 


1.15 


1.13 


1.11 


1.09 


1.07 


1.05 


392 


1.24 


1.23 


1.21 


1.19 


1.17 


1.15 


1.13 


1.11 


1.09 


1.07 


1.06 


410 


1.25 


1.23 


1.22 


1.20 


1.18 


1.16 


1.14 


1.12 


1.10 


1.08 


1.06 


428 


1.25 


1.24 


1.22 


1.20 


1.18 


1.16 


1.14 


1.1.2 


1.11 


1.09 


1.07 



There are two distinct types of heaters in which heat is derived 
from exhaust steam. These are known as closed and open 
heaters. Each has its advantages and disadvantages. The 
closed heater is constructed so that the water is forced under pres- 



HANDBOOK ON ENGINEERING. 681 

sure through tubes or chambers surrounded by the exhaust steam, 
the heat being transmitted through the walls of the tubes and cham- 
bers. The open heater is a vessel in which the feed water comes 
into direct contact with the exhaust steam, by spraying or inter- 
mingling. The heated water is pumped hot into the boiler. 
The closed heater has the advantage of permitting the water to 
pass through the pump cold and in that state is easily handled. 
To pump hot water from an open heater requires special care in 
piping and packing the feed-pump. The closed heater, being a 
purifier (if any lime is present in water, a portion is bound to be 
precipitated by heat), should be cleaned, a job about as difficult 
as cleaning a boiler ; or blown out, which is never a satisfactory 
method. In the precipitation of lime by heat, carbonic acid gas 
is set free and chemists say that this gas in a nascent state (just 
being born) attacks iron and brass. Whatever the cause, experi- 
ence has demonstrated that ordinary wrought iron, steel and 
brass, corrode under this action. The open heater, being usually 
a large chamber, is accessible for cleaning out, and if made with 
ordinary care will last a long time. A leak in it is not a serious 
matter, while a leak in the closed heater means a waste of hot 
water into the exhaust pipe. The open heater has, at times, 
been the cause of serious mishaps. In it the steam and water 
mix ; with any stoppage in exit of feed-water, there is danger 
of flooding the cylinder of the steam engine through exhaust 
pipe, causing a wreck. The more modern forms of these heaters 
and the experience obtained in their use have reduced this 
difficulty to a minimum. 

WATER. 

Pure water at 62° F. weighs 62.355 pounds per cubic foot, or 
8i lbs. per U. S. gallon; 7.48 gallons equal 1 cu. ft. It takes 
30 lbs., or 3.6 gal. for each horse-power per hour. It would be 
difficult to getat the total daily horse-power of steam used in the 



682 HANDBOOK ON ENGINEERING. 

U. S., but it reaches into the billions of gallons of feed water per 
day. The importance of knowing what impurities exist in most 
feed waters, how these act on a boiler and how they may be re- 
moved is, therefore, patent to every intelligent engineer. I give 
therefore, the thoughts of some prominent investigators on the 
subject. 

Prof* Thurston says : — 

" Incrustation and sediment are deposited in boilers, the one 
by the precipitation of mineral or other salts previously held in 
solution in the feed-water, the other by the deposition of mineral 
insoluble matters, usually earths, carried into it in suspension or 
mechanical admixture. Occasionably also, vegetable matter of a 
glutinous nature is held in solution in the feed water, and, pre- 
cipitated by heat or concentration, covers the heating surfaces 
with a coating almost impermeable to heat, and hence, liable to 
cause an overheating that may be very dangerous to the struc- 
ture. A powdery mineral deposit sometimes met with is equally 
dangerous, and for the same reason. The animal and vege- 
table OILS AND GREASES CARRIED OVER FROM THE CONDENSER OR 
FEED WATER HEATER ARE ALSO VERY LIKELY TO CAUSE TROUBLE. 

Only mineral oils should be permitted to be thus introduced, and 
that in minimum quantity. Both the efficiency and safety of the 
boiler are endangered by any of these deposits. 

" The amount of the foreign matter brought into the steam 
boiler is often enormously great. A boiler of 100 horse-power 
uses, as an average, probably a ton and a half of water per 
hour, or not far from 400 tons per month, steaming ten hours 
per day ; and even with the water as pure as the Croton at 
New York, receives 90 pounds of mineral matter, and from 
many spring waters a ton, which must be either blown out or 
deposited. These impurities are usually either calcium carbon- 
ate or calcium sulphate, or a mixture ; the first is most com- 
mon on land, the second at sea. Organic matters often 



HANDBOOK ON ENGINEERING. 683 

harden these mineral scales and make them more difficult of 
removal. 

' ' The only positive and certain remedy for incrustation and 
sediment, once deposited, is periodical removal by mechanical 
means at sufficiently frequent intervals to insure against injury by 
too great accumulation. Between times, some good may be done 
by special expedients suited to the individual case. No one 
process and no one antidote will suffice for all cases. 

" Where carbonate of lime exists, sal-ammoniac may be used 
as a preventive of incrustation, a double decomposition occur- 
ring resulting in the production of ammonia carbonate and 
calcium chloride — both of which are soluble, and the first of 
which is volatile. The bicarbonate may be in part precipitated 
before use by heating to the boiling point, and thus breaking 
up the salt and precipitating the insoluble carbonate. Solutions 
of caustic lime and metallic zinc act in the same manner. 
Waters containing tannic acid and the acid juices of oak, 
sumach, logwood, hemlock, and other woods, are sometimes 
employed, but are apt to injure the iron of the boiler, as may 
acetic or other acid contained in the various saccharine matters 
often introduced into the boiler to prevent scale, and which 
also make the lime-sulphate scale more troublesome than when 
clean. Organic matter should never be used. 

' ' The sulphate scale is sometimes attacked by the carbonate of 
soda, the products being a soluble sodium sulphate and a pulver- 
ulent insoluble calcium carbonate, which settles to the bottom like 
other sediments and is easily washed off the heating surfaces. 
Barium chloride acts similarly, producing barium sulphate and 
calcium chloride. All the alkalies are used at times to reduce 
incrustations of calcium sulphate, as is pure crude petroleum, the 
tannate of soda and other chemicals. 

" The effect of incrustation and of deposits of various kinds, is 
to enormously reduce the conducting power of heating surfaces ; 



684 HANDBOOK ON ENGINEERING. 



3iency of 



so much so, that the power, as well as the economic efficiency i 
a boiler, may become very greatly reduced below that for which it 
is rated, and the supply of steam furnished by it may become 
wholly inadequate to the requirements of the case. 

"It is estimated thatyL of an inch (0.16 cm.) thickness of 
hard ' scale ' on the heating surface of a boiler will cause a waste 
of nearly one- eighth of its efficiency, and the waste increases as the 
square of its thickness. The boilers of steam vessels are 
peculiarly liable to injury from this cause where using salt water, 
and the introduction of the surface condenser has been thus 
brought about as a remedy. Land boilers are subject to incrus- 
tation by the carbonate and other salts of lime and by the deposit 
of sand or mud mechanically suspended in the feed- water. 

THE TEMPERATURE AND PRESSURE OF SATURATED 
STEAM. 

The accompanying diagram and explanation, taken from that 
excellent publication, The Locomotive , will be found much more 
convenient for reference than steam tables. The description says 
that one of the most fundamental and best known facts in steam 
engineering is that saturated steam has a certain definite tem- 
perature for each and every definite pressure ; and in all books 
on steam we find tables of corresponding temperatures and pres- 
sures, by the use of which we are enabled to find out what 
the temperature of the .steam is when we know what the pres- 
sure is, and vice versa. For accurate work these tables are all 
right ; but when (as is usually the case) we do not need to 
know either the temperature or the pressure with any very 
great precision, a diagram which presents the facts directly to 
the eye is much more convenient. Such a diagram is presented 
herewith. On the left-hand side of each vertical line I have 
marked the pressures, and on the right-hand side of the same 
lines I have marked the corresponding temperatures. The pres- 



HANDBOOK ON ENGINEERING. 



■685 



50- 



45- 



40—: 



35- 



30- 



25- 



20- 



—255 
—275' 



-295' 



-290' 



100- 

Ihs 



35—. 



90- 



-270' 



80- 



75- 



—265 
—-2S0' 



70— 



- — 255' 



-250" 65— 
-245' 

Jr-r240° go 

-E-2J5" 

-2J0° 

_E-Z25 

"E-220' 



55- 



1U 
0- 



2/5° 71 s 
212° 50— J 



-335* 



-330* 



-325' 



/50— i 



'45— 



140- 



—3$0' 



/35 — 



/30 — 



— 355 



—320' lZ5 — 



-315' 



- — 310° 



-305" 



izo- 



U5 — 



110- 



-3G0 



Us 

100- 



£0Gh-n 



-365' 



135 — 



—385' 



/SO- 



185- 



— 380° 



ISO — 



175— 



-350' 



-345' 



170- 



/65- 



160- 



105— -T 155— 

-340' 



lis - 

150 



—375' 



-370° 



COMPARATIVE DIAGRAM SHOWING THE TEMPERATURE AND 
OF SATURATED STEAM. 



b$b HANDBOOK ON ENGINEERING. 

sures are all gauge pressures, that is, they represent the direct 
gauge reading or pressure above that of the atmosphere. The 
temperatures are on the Fahrenheit scale. The diagram is based 
upon Prof. Cecil H. Peabody's steam tables, and we have 
assumed that the average atmospheric pressure is 14.70 pounds 
per square inch. 

A few examples will make the use of the diagram clear: (1) 
What is the temperature of saturated steam when its pressure, 
above the atmosphere, is 75 pounds per square inch? Ans. We 
find 75 pounds on the left-hand side of the second vertical line, 
and looking on the other side of the line we see that the corre- 
sponding temperature is just a fraction of a degree less than 320 
degrees Fahr. (2) What is the temperature of saturated steam 
when its pressure, above the atmosphere, is 197 lbs. per square 
inch? Ans. We find 197 lbs. on the left-hand side of the last 
vertical line. It is not marked in figures, but 195 is so marked, 
and 197 is two divisions higher than 195. Looking opposite to 
197 we see that the corresponding temperature is about half way 
between 386 degrees and 387 degrees. Hence, we conclude that 
the temperature of saturated steam at the given pressure is about 
3861°. (3) When the temperature of saturated steam is 227°, 
what is its pressure? Ans. We find 227° on the right-hand 
side of the first line, two divisions above 225° ; and looking 
opposite to it, we see that the gauge pressure corresponding to 
this temperature is almost exactly five pounds. (4) When the 
temperature of saturated steam is 363°, what is its pressure? 
Ans. We find 363° on the right-hand side of the third vertical 
line, three divisions above 360°, and looking on the other side of 
the vertical line, we see that the corresponding gauge pressure is 
about 144^ lbs. to the square inch. 

SOMETHING FOR NOTHING. 

In the first place, it should be remembered that in mechanics 
the measure of work done is the foot pound, a term which defines 



HANDBOOK ON ENGINEERING. 



687 



itself. A foot pound of work is the amount of energy required to 
lift one pound one foot high. A foot pound, therefore, is the 
product of force and distance, force being simply a push or a 
pull. A machine can be made to increase the acting force, as 
is seen in the case of a crane, where the weight lifted is much 
greater than the force applied at the handle by the operator. It 
is also possible to increase the distance moved by some part of a 
machine, but it must be done by applying a greater force as in 
the case of a steam engine, where the distance moved by the belt 
is greater than the space passed over by the piston, but the total 
pressure of the steam against the piston is greater than the 
effective pull exerted by the belt. 



Melting Points of Metals and Solids. 



Antimony 


melts at 


Bismuth 


" 


Brass 


" 


Cadmium 


" 


Cast Iron 


(C 


Copper 


a 


Glass 


a 


Gold 


ei 


Lead 


u 


Ice 


a 



Deg. Fahr. \ 




. 951 ; 




. 476 




. 1900 




. 602 


. 1890 


to 2160 




. 1890 




. 2377 




. 2250 




. 594 




. 32 





Deg. Fahr. 


Platinum melts at 


. . . 4580 


Potassium " 


... 135 


Saltpeter " 


... 600 


Steel " 


2340 to 2520 


Sulphur u 


... 225 


Silver u 


. . . 1250 


Tin « 


... 420 


Wrought Iron 


2700 to 2880 


Zinc " 


... 740 


Aluminum " 


. . . 1260 



In both the crane and the steam engine, however, the applied 
force multiplied by the distance through which it moves in a given 
time, must be enough greater than the product of the force at the 
crane hook or the rim of the fly-wheel, and the distance through 



688 HANDBOOK ON ENGINEERING. 

which it moves to make up for the loss through friction in the 
machine itself. The foot pounds of work done by any machine 
whatever must always be less than the foot pounds put into the 
machine in the same length of time. A study of this principle 
and of the methods of applying it, is all that is necessary to 
enable one to decide upon the soundness of the claims made for 
any power multiplying device. A British Thermal Unit (B. T. 
U.) is the amount of heat required to raise the temperature of a 
pound of water 1° Fahr., and its dynamic value is 778 lbs. raised 
to a height of one foot. 

CHIMNEYS. 

Chimneys are required for two purposes : 1st, to carry off 
obnoxious gases; 2d, to produce a draft, and so facilitate com- 
bustion. The first requires size, the second height. Each pound 
of coal burned yields from 13 to 30 pounds of gas, the volume of 
which varies with the temperature. The weight of gas to be car- 
ried off by a chimney, in a given time, depends on three things — 
size of chimney, velocity of flow and density of gas. But as the 
density decreases directly as. the absolute temperature, while the 
velocity increases with a given height, nearly as the square root 
of the temperature, it follows that there is a temperature at which 
the weight of gas delivered is a maximum. This is about 550° 
above the surrounding air. Temperature, however, makes so 
little difference that at 550° above the quantity is only 4 per cent 
greater than at 300°. Therefore, height and area are the only 
elements necessary to consider in an ordinary chimney. The in- 
tensity of draft is, however, independent of the size, and depends 
upon the difference in weight of the outside and inside columns of 
air, which varies nearly as the product of the height into the 
difference of temperature. This is usually stated in an equiva- 
lent column of water, and may vary from to possibly 2 inches. 
After a height has been reached to produce draft of sufficient 



HANDBOOK ON ENGINEERING. 



689 




690 , HANDBOOK ON ENGINEERING. 

intensity to burn fine, hard coal, provided the area of the chimney 
is large enough, there seems no good mechanical reason for add- 
ing further to the height, whatever the size of the chimney 
required. Where cost is no consideration, there is no objection 
to building as high as one pleases ; but for the purely utilitarian 
purpose of steam-making, equally good results might be attained 
with a shorter chimney at much less cost. The intensity of draft 
required varies with the kind and condition of the fuel and the 
thickness of the fires. Wood requires the least, and fine coal or 
slack the most. To burn anthracite slack to advantage, a draft 
of 1J inch of water is necessary, which can be attained by a well- 
proportioned chimney 175 feet high. Generally, a much less 
height than 100 feet cannot be recommended for a boiler, as the 
lower grades of fuel cannot be burned as they should be with a 
shorter chimney. 

The proportioning of chimneys is very largely a matter of expe- 
rience and judgment. Various rules have been formulated for 
this purpose, but they all vary more or less. A chimney must 
have sufficient cross-section to easily carry off the products of 
combustion, and be high enough to produce sufficient draft for 
complete and rapid combustion. Where there is a choice between 
a high narrow stack and a lower wide one, the nature of the fuel 
should decide the matter ; as a rule, the taller stack is preferable. 
The amount of fuel to be burnt per square foot of grate per hour 
has been increasing in modern practice ; therefore, the old rules do 
not fit the case any more. Then again, it makes a difference how 
many boilers are to run into the same chimney. The heaviest 
work of the chimney is immediately after firing, since the friction 
through the fresh coal is greater and the temperature less then 
than some minutes later. But it would be bad practice to fire all 
boilers or all doors simultaneously. Hence, the second boiler 
does not require as much area as the first ; say, 75 per cent will 
do. After that there comes the additional consideration that as 



HANDBOOK ON ENGINEERING. 



691 



^«^&- 




692 



HANDBOOK ON ENGINEERING. 



the diameter of the stack increases, the friction in stack and 
breeching decreases rapidly. Therefore, for the third and each 
succeeding boiler, 50 per cent of the first area will suffice. But 
as more are added, the height should be increased, more espe- 
cially if the horizontal flue from boiler to stack increases in length, 
as it usually will. A good rule is to make the height 25 times 
the diameter, with possibly a gradual decrease in the ratio to 20 
times the diameter for the larger chimneys. Thus a 4-foot diame- 
ter would call for 100-feet height, and a 5-foot, for 120-feet, a 
6-foot for 140-feet, and a 10-foot for 200-feet height. 

TABLE OF SIZES OF CHIMNEYS. 





Diameter and Nominal Horse Power. 


°3 
trj 


20" 


26" 


30" 


34" 


36" 


40" 


44" 


50" 


54" 


58" 


60" 


64" 


72" 


78" 


70 ft. 


40 

50 


60 

75 


























80 ft. 


100 
120 


130 

150 


150 
175 


175 

200 


200 
225 
250 
















90 ft. 


300 
340 
360 














100 ft. 


375 
400 
425 


430 
455 
500 


500 
550 
600 


600 
650 
700 


750 

825 
900 


930 


110 ft. 














990 


120 ft. 
















1050 























IRON CHIMNEY STACKS. 

In many places iron stacks are preferred to brick chimneys. 
Iron chimneys are bolted down to the base so as to require no 
stays. A good method of securing such bolts to the stack is 
shown in detail in the figure on page 693. Iron stacks require to be 
kept well painted to prevent rust, and generally, where not bolted 
down, as here shown, they need to be braced by rods or wires to 
surrounding objects. With four such braces attached to an 
angle iron ring at f the height of stack, and spreading laterally at 



HANDBOOK ON ENGINEERING. 



693 



least an equal distance, each brace should have an area in square 
inches equal to y^-^ the exposed area of stack (dia. x height) in 
feet. Stability or power to withstand the overturning force of 




Holding down Bolts and Lugs. 



the highest winds, requires a proportionate relation between the 
weight, height, breadth of base, and exposed area of the chimney. 
This relation is expressed in the equation 



G- 



dh* 



= TT, 



in which d equals the average breadth of the shaft ; h = its 
height ; b — the breadth of base — all in feet ; W = weight of 
chimney in lbs., and C = a coefficient of wind pressure per 



694 



HANDBOOK ON ENGINEERING. 



square foot of area. This varies with the cross-section of the 
chimney, and = 56 for a square, 35 for an octagon and 28 for a 
round chimney. Thus a square chimney of average breadth of 
8 feet, 10 feet wide at base and 100 feet high, would require to 
weigh 56x8x100x10=448,000 lbs., to withstand any gale 
likely to be experienced. Brickwork weighs from 100 to 130 
lbs. per cubic foot; hence, such a chimney must average 13 
inches thick to be safe. A round stack could weigh half as 
much, or have less base. 

WEIGHT OF SHEET LAP RIVETED STEEL SMOKE STACKS, 
PER FOOT. 



THICKNESS. 





No. 


No. 


Xo. 


Xo. 


Xo. 


^o. 


.3.-" 


_7_" 


1" 


_Q." 


A" 

52| 


LL" 


I" 
63 


L3." 


.1." 


IV 


1" 


DIA. 


18 


16 


]4 
13 


12 
17 


10 
21 


8 
26} 


1 6 

31J 


32 

37 


4 
42 


3 2 
47 


32 

58 


3 2 

68} 


16 

73.! 


32 

75} 


•i 


12" 


8 


10 


84 


14" 


91 


11| 


151 


20 


21 I 


29J 


36} 


42 


48.| 


54 \ 


62i 


67 


m 


79} 


85 


91 


97 


16" 


104 


13 


in 


23 


28 


34 


42 


49 


56 


63 


70 


77 


84 


91 


98 


105 


112 


18" 


Hi 


14£ 


19| 


26 


311 


38} 


47 


55 


63 


71 


79 


S6 


94 


102 


110 


118 


126 


20" 


13 


16 


22 


2^ 


35 


424 


52 


60 


69 


78 


86 


95 


104 


113 


121 


131 


138 


22" 


14J 


17} 
19J 


24} 


311. 


38| 


46| 


54 


63i 


73 


82 


91 


99 


108 


118 


127 


137 


14 6 


24" 


15* 


26| 


34} 


42 


51 


59 


68| 


78! 


88 


98 


108 


118 


128 


137 


147 


157 


26" 


16f 


21 


28} 


37 


45£ 


55} 


63 


73.i 


84 


94 


105 


115 


126 


137 


147 


158 


168 


28" 


18 


22| 


31 


40 


49 




67 


78 


89! 


100 


111 


122 


134 


145 


156 


167 


179 


20" 




24* 


33 


42} 


52 \ 


63} 


71 


83 


95" 


L06i 


118 


130 


142 


154 


166 


178 


190 


32" 




26J 


35 


45| 


56 


68 


75 


87^ 


100.| 


113 


125 


138 


150 


163 


175 


188 


201 


34" 




28 


37 


48} 


59.i 


72} 


80 


93 


106 


119 


132 


146 


160 


173 


186 


199 


212 


36" 




29f 


39 


51 


63 


764 


85 


100 


114 


128 


143 


158 


173 


188 


202 


216 


230 


38" 




31? 


411 


.; 


66! 


80} 


90 


105 


120 


135 


151 


166 


182 


198 


213 


227 


242 


40" 




3:4 


434 


56£ 


70 


85 


94 


110 


126 


142 


158 


174 


191 


208 


224 


239 


254 


42" 




35 


45| 


5;»i 


73i 


m 


98 


115 


132 


149 


166 


183 


200 


217 


234 


250 


266 


44" 




36} 


48 


62 


77" 


93A 


103 


121 


138 


155 


173 


191 


209 


227 


245 


262 


279 


48" 




3Si 


501 


65 


80S 


. 


107 


126 


144 


162 


181 


199 


218 


237 


255 


273 


291 


48" 




40 


52| 


68 


84 


102 


112 


131 


150 


169 


188 


208 


227 


247 


266 


284 


303 


50" 






54} 

57 


71 
74 

77 


87* 
91 
94* 


106} 

uoI 

114} 


116 
121 

124 


136 
142 
147 


156 
162 

168 


176 
182 

1S9 


195 
203 
211 


216 
224 
233 


236 
245 
254 


25 S 
266 
276 


277 
287 
298 


296 
307 
319 


315 


52" 






328 


54" 






349 


56" 








80 


98 


119 


133 


158 


180 


202 


225 


248 


270 


294 


317 


340 


363 


58" 








83 


102 


123} 


137 


164 


186 


209 


232 


256 


280 


304 


327 


351 


375 


60" 








86 
89 
92 


106 
110 
114 


1274 
131} 
136 


142 
146 
151 


169 
174 
179 


192 
198 
204 


215 
222 
229 


240 
247 
255 


264 

273 
281 


289 
298 
307 


314 
324 
333 


338 
349 
359 


362 
374 

3S5 


387 


62" 








400 


64" 








412 













HANDBOOK ON ENGINEERING. 695 

CHAPTER XXIV. 
HORSE=POWER OF GEARS. 

To determine the horse-power which any gear-wheel will trans- 
mit, four facts are required to be known : — 

1st. The kind of wheel, whether spur, bevel, spur mortise, or 
bevel mortise. 2d. The pitch. 3d. The face. 4th. The velocity 
of pitch circle in feet per second. 

Generally, the fourth fact is not known. It can be found if 
the pitch diameter of the wheel in inches and the number of revo- 
lutions per minute are given, for it can be obtained from them by 
the following rule : — 

Rale* — Given the pitch diameter in inches and the number of 
revolutions per minute ; to find the velocity of pitch line in feet 
per second. 

First, multiply the pitch diameter (in inches) by the number 
of revolutions per minute. Second, divide the product thus found 
by 230. The quotient is the velocity required. 

Example. — What is the velocity of the pitch circle of a 
gear-wheel in feet per second, the pitch diameter == 43 inches, 
the revolutions per minute = 125 ? 

43 x 125 divided by 230 == 23.4 feet per second. 

Table \ shows the greatest horse-power which different kinds 
of gears of 1-inch pitch and 1-inch face will safely transmit at 
various pitch-line velocities. To find the greatest horse-power 
which any other pitch and face will safely transmit, the following 
rule can be used : — 

Rule* — Given, the pitch (in inches), face (in inches), velocity 
of pitch circle (in feet per second) , and kind of gear ; to find the 
greatest horse-power that can be safely transmitted. 

First. Find the horse-power in Table 2, which the given kind 



696 



HANDBOOK ON ENGINEERING. 



of wheel with 1-inch pitch and 1-inch face will transmit at the 
given velocity. Second. Multiply the pitch by the face. Third. 
Multiply the horse-power found by the product of pitch by face. 
The final product is the horse-power required. 

Example. — What is the greatest horse-power that a bevel- 
wheel, 43" pitch diameter, 2" pitch, 6" face, and 125 revolutions' 
per minute will safely transmit? 

From previous example, we have found the pitch-line velocity 
to be 23.4 feet per second, which is nearest to a velocity of 24 
feet per second in Table 1. 

First, the horse-power which a bevel wheel of 1" pitch and 1' 
face will transmit is (from table) at this velocity 4.931. 

Second, the product of pitch by face is 2 x 6 = 12. 

Third, 12 x 4.931 =59. 17 horse-power. Answer. 

Whenever it is desirable to know about the average horse- 
power that any wheel will transmit, |- or J of the results obtained 
by the rule above should be taken. 

TABLE 1. — TABLE SHOWING THE HORSE-POWER WHICH DIFFERENI 
KINDS OF GEAR WHEELS OF ONE INCH PITCH AND ONE INCH FACE 
WILL TRANSMIT AT VARIOUS VELOCITIES OF PITCH CIRCLE. 



1 


2 


3 


i 


5 


Velocity of 
- pitch circle in 
ft. per sec. 


Spur Wheels. 


Spur Mortise 
Wheels. 


Bevel Wheels. 


Bevel 
Mortise 
Wheels. 



2 


1.338 


.647 


.938 


.647 


. 3 


1.756 • 


.971 


1.227 


.856 


6 


2.782 


1.76 


1.76 


1.363 


12 


4.43 


3.1 


3.1 


2.16 


18 


5.793 


4.058 


4.058 


2.847 


24 


7.052 


4.931 


4.931 


3.447 


30 


8.182 


5.727 


5.727 


4.036 


36 


9.163 


6.314 


6.414 


4.516 


42 


10.156 


7.102 


7.102 


4.963 


48 


10.083 


7.680 


7.680 


5.411 



HANDBOOK ON ENGINEERING. 



697 



Note. — When velocities are given, which are between these 
in Table, the horse-power can be found by interpolation. 

Thus, the horse-power for spur wheels at 14 feet velocity is 
found as follows : — 



] X 5.793 minus 4.43= 1.363. 
Then f of 1.363 == .454 and .454 -f 4.43 — 4.884 horse-power. 



14 minus 12 = 2 ~ 
18 " 12 = 6. 



TABLE 2. — SHAFTING, — HORSEPOWER TRANSMITTED BY VARIOUS 
SHAFTS, AT 100 REVOLUTIONS PER MINUTE UNDER VARIOUS CON- 
DITIONS. 



Diameter 
of Shaft. 



Line 
Shafts. 



Shaft as 
a Prime 
Mover. 



4 


1 


2 


3 


Shafts 
Under 
Slight 
Bending 
Strain. 


Diameter 
of Shaft. 


Line 

Shafts. 


Shaft as 
a Prime 
Mover. 



Shafts 
Under 
Slight 
Bending 
Strain. 



W 
W 

Hi" 

m" 
w 

2iV 

m" 

2 ii" 

3-iV 



.7 
1.3 
2.4 
3.8 
5.8 
8.3 

11.5 

15.5 

20. 

26. 

33. 



.4 
.7 
1.2 
1.9 
2.9 
4.2 
5.8 
7.8 

10. 

13. 

17. 



1.3 

2.6 
4.7 
7.6 

11.5 

16.6 

23. 

31. 

40. 

51. 

65. 





40. 


20. 


49. 


25. 


w 


70. 


35. 


m ,f 


96. 


48. 


K-7 " 


126. 


64. 


Hi" 


167. 


84. 


fit" 


266. 


133. 


nr 


399. 


200. 


w 


570. 


285. 


9i|" 


783. 


392. 



80- 
97. 

139. 

192. 

256. 

334. 

532. 

797. 
1139. 
1566. 



This table states the horse-power that various sizes of shafts 
will safely transmit at 100 revolutions per minute under various 
conditions. 

Prime movers are those shafts in which the variation above 
and below the average horse-power transmitted is great, also 
where the transverse strain due to belts or heavy pulleys is large, 
such as jack-shafts, crank-shafts, etc. 



698 HANDBOOK ON ENGINEERING. 

WHEEL GEARING. 

The pitch line of a wheel is the circle upon which the pitch 
is measured, and it is the circumference by which the diameter, 
or the velocity of the wheel, is measured. The pitch is the arc 
of the circle of the pitch line, and is determined by the num- 
ber of teeth in the wheel. The true pitch (chordal), or that 
by which the dimensions of the tooth of a wheel are alone 
determined, is a straight line drawn from the centers of two 
contiguous teeth upon the pitch line. The line of centers is 
the line between the centers of two wheels. The radius of a 
wheel is the semi-diameter running to the periphery of a tooth. 
The pitch radius is the semi-diameter running to the pitch line. 
The length of a tooth is the distance from its base to its ex- 
tremity. The breadth of a tooth is the length of the face of 
wheel. The teeth of wheels should be as small and numerous 
as is consistent with strength. When a pinion is driven by 
a wheel, the number of teeth in the pinion should not be 
less than eight. When a wheel is driven by a pinion, the 
number of teeth in the pinion should not be less than ten. 
The number of teeth in a wheel should always be prime to the 
number of the pinion ; that is, the number of teeth in the 
wheel should not be divisible by the number of teeth in the 
pinion, without a remainder. This is in order to prevent the 
same teeth coming together so often as to cause an irregular 
wear of their faces. An odd tooth introduced into a wheel is 
termed a hunting-tooth or cog. 

TO COMPUTE THE PITCH OF A WHEEL. 

Rule* — Divide the circumference at the pitch-line by the num- 
ber of teeth. 

Example. — Awheel 40 in. in diameter, requires 75 teeth; 
what is its pitch ? 

3.1416x40 , fl _ KK . 

_ = 1.6755 in. 

75 



HANDBOOK ON ENGINEERING. 699 

TO COMPUTE THE CHOEDAL PITCH. 

R u le^ — Divide 180° by the number of teeth, ascertain the sin. 
of the quotient, and multiply it by the diameter of the wheel. 

Example. — The number of teeth is 75 and the diameter 40 
in. ; what is the true pitch ? 

1?^. = 2° 24' and sin. of 2° 24' = .04188, which x 40 = 1.6752 in. 
75 

TO COMPUTE THE DIAMETER OF A WHEEL. 

Rule, — Multiply the number of teeth by the pitch, and divide 
the product by 3.1416. 

Example. — The number of teeth in awheel is 75, and the 
pitch 1.675 in. ; what is the diameter of it? 
75 x 1.675 



3.1416 



: 40 in. 



TO COMPUTE THE NUMBER OF TEETH IN A WHEEL. 

R u l e „ — Divide the circumference by the pitch. 

TO COMPUTE THE DIAMETER WHEN THE TRUE PITCH IS GIVEN. 

R u l e . — Multiply the number of teeth in the wheel by the true 
pitch, and again by .3184. 

Example. — Take the elements of the preceding case. 
75 x 1.6752 x .3184 = 40 in. 

TO COMPUTE THE NUMBER OF TEETH IN A PINION OR FOLLOWER TO 
HAVE A GIVEN VELOCITY. 

R u fe # __ Multiply the velocity of the driver by its number of 
teeth, and divide the product by the velocity of the driven. 

Example. — The velocity of a driver is 16 revolutions, the 
number of its teeth 54, and the velocity of the pinion is 48 ; what 
is the number of its teeth ? 

16 x 54 1£) , ,, 

= 18 teeth. 

48 



700 HANDBOOK ON ENGINEERING. 

2. A wheel having 75 teeth is making 16 revolutions per min- 
ute. What is the number of teeth required in the pinion to make 
24 revolutions in the same time ? 
16 x 75 



24 



= 50 teeth. 



TO COMPUTE THE PROPORTIONAL RADIUS OF A WHEEL OR PINION. 

Rule* — Multiply the length of the line of centers by the num- 
ber of teeth in the wheel for the wheel, and in the pinion for the 
pinion, and divide by the number of teeth in both the wheel and 
the pinion. 

TO COMPUTE THE DIAMETER OF A PINION, WHEN THE DIAMETER OF 
THE WHEEL AND NUMBER OF TEETH IN THE WHEEL AND PINION 
ARE GIVEN. 

Rule* — Multiply the diameter of the wheel by the number of 
teeth in the pinion, and divide the product by the number of teeth 
in the wheel. 

Example. — The diameter of awheel is 25 in., the number of 

its teeth 210, and the number of teeth in the pinion 30 ; what is 

the diameter of the pinion ? 

25x30 Q " 

: 3.57 in. 



210 



TO COMPUTE THE CIRCUMFERENCE OF A WHEEL. 

Rule* — Multiply the number of teeth by their pitch. 

TO COMPUTE THE REVOLUTIONS OF A WHEEL OR PINION. 

Rule* — Multiply the diameter or circumference of the wheel or 
the number of its teeth, as the case may be, by the number of its 
revolutions, and divide the product by the diameter, circumfer- 
ence, or number of teeth in the pinion. 

Example. — A pinion 10 in. in diameter is driven by a wheel 



HANDBOOK ON ENGINEERING. 701 

2 ft, iu diameter, making 46 revolutions per minute ; what is the 
number of revolutions of the pinion ? 
2 x 12x46 



10 



110.4 revolutions. 



TO COMPUTE THE VELOCITY OF A PINION. 

Rule* — Divide the diameter, circumference or number of teeth 
in the driver, as the case may be. by the diameter, etc., of the 
pinion. 

WHEN THERE IS A SERIES OR TRAIN OF WHEELS AND PINIONS. 

Rule* — Divide the continued product of the diameter, circum- 
ference, or number of teeth in the wheels by the continued 
product of the diameter, etc., of the pinions. 

Example. — If a wheel of 32 teeth drive a pinion of 10, upon 

the axis of which there is one of 30 teeth, driving a pinion of 8, 

what are the revolutions of the last? 

32 30 960 

— x — == -j— =12 revolutions. 

Ex. 2. — The diameters of a train of wheels are 6, 9, 9, 10 and 

12 in. ; of the pinions, 6, 6, 6, 6, and 6 in. ; and the number of 

revolutions of the driving shaft or prime mover is 10 ; what are 

the revolutions of the last pinion ? 

6x9x9x10x12x10 583200 '• 

ib revolutions. 



6x6x6x6x6 7776 

TO COMPUTE THE PROPORTION THAT THE VELOCITIES OF THE WHEELS 
IN A TRAIN WOULD BEAR TO ONE ANOTHER. 

Rule* — Subtract the less velocity from the greater, and divide 
the remainder by one less than the number of wheels in the train ; 
the quotient is the number, rising in arithmetical progression from 
the less to the greater velocity. 



702 HANDBOOK ON ENGINEERING. 

Example. — What should be the velocities of three wheels to 
produce 18 revolutions, the driver making 3 ? 

— — 7.5 = number to be added to velocity of the 
3 minus 1=2 

driver = 7.5 + 3 = 10.5 and 10.5 -f 7.5 = 18 revolutions. 

Hence, 3, 10.5 and 18 are the velocities of the three wheels. 

GENERAL ILLUSTRATIONS. 

1. A wheel 96 inches in diameter, having 42 revolutions per 

minute, is to drive a shaft 75 revolutions per minute, what should 

be the diameter of the pinion ? 

96x42 KO ' . 
=53.76 in. 

75 

2. If a pinion is to make 20 revolutions per minute, required 
the diameter of another to make 58 revolutions in the same time. 
58 divided by 20 = 2.9 = the ratio of their diameters. Hence 
if one to make 20 revolutions is given a diameter of 30 in., the 
other will be 30 divided by 2.9 == 10.345 in. 

3. Required the diameter of a pinion to make 12| revolutions 

in the same time as one of 32 in. diameter making 26. 

32x26 aa Ka . 

66.56 in. 

12.5 

4. A shaft having 22 revolutions per minute, is to drive another 
shaft at the rate of 15, the distance between the two shafts upon 
the line of centers is 45 in. ; what should be the diameter of the 
wheels ? 

Then, 1st, 22 -j- 15 : 22 : : 45 : 26.75 finches in the radius of 
the pinion. 

2d. 22 -f 15 : 15 : : 45 : 18.24 = inches in the radius of the spur. 

5. A driving shaft, having 16 revolutions per minute, is to 
drive a shaft 81 revolutions per minute, the motion to be com- 
municated by two geared wheels and two pulleys, with an inter- 
mediate shaft ; the driving wheel is to contain 54 teeth, and the 



HANDBOOK ON ENGINEERING. 703 

driving pulley upon the driven shaft is to be 25 in. in diameter ; 
required the number of teeth in the driven wheel, and the diameter 
of the driven pulley. Let the driven wheel have a velocity of 
V 16x81=36 a mean proportional between the extreme veloci- 
ties 16 and 81. 

Then, 1st, 36 : 16 : : 54 : 24 = teeth in the driven wheel. 

2d. 81: 36:: 25: 11. 11= inches diameter of the driven pulley. 

6. If , as in the preceding case, the whole number of revolutions 
of the driving shaft, the number of teeth in its wheel and the 
diameter of the pulley are given, what are the revolutions of the 
shafts ? 

Then, 1st, 18 : 16 : : 54 : 48 = revolutions of the intermediate 
shaft. 

2d. 15 : 48 : : 25 : 80 = revolutions of the driven shaft. 

TO COMPUTE THE DIAMETER OF A WHEEL FOR A GIVEN PITCH AND 
NUMBER OF TEETH. 

Rule* — Multiply the diameter in the following table for the 
number of teeth by the pitch, and the product will give the diam- 
eter at the pitch circle. 

Example. — What is the diameter of a wheel to contain 48 
teeth of 2.5 in. pitch? 

15.29x2.5 = 38.225 in. 

TO COMPUTE THE PITCH OF A WHEEL FOR A GIVEN DIAMETER AND 
NUMBER OF TEETH. 

Rule* — Divide the diameter of the wheel by the diameter in 
the table for the number of teeth, and the quotient will give the 
patch. 

Example. — What is the pitch of a wheel when the diameter of 
it is 50.94 in., and the number of its teeth 80? 
50.94 
25^7 = 2in - 



704 



HANDBOOK ON ENGINEERING. 



PITCH OF WHEELS. 

TABLE WHEREBY TO COMPUTE THE DIAMETER OF A WHEEL FOR A 
GIVEN PITCH, OR THE PITCH FOR A GIVEN DIAMETER. 

From 8 to 192 teeth. 



«t-< 05 
O 05 

6 H 
53 


05 

05 
S 

05 


2.61 


O 05 

53 
45 


i 

05 

s 

5 

14.33 


53 

82 


S 

5 

26.11 


O 05 

53 


05 
05 

i 

Q 


S- 05 

3* 

53 
156 


05 

5 

5 


8 


119 


37.88 


49.66 


9 


2.93 


46 


14.65 


83 


26.43 


120 


38.2 


157 


49.98 


10 


3.24 


47 


14.97 


84 


26.74 


121 


38.52 


158 


50.3 


11 


3.55 


48 


15.29 


85 


27.06 


122 


38.84 


159 


50.61 


12 


3.86 


49 


15.61 


86 


27.38 


123 


39.16 


160 


50.93 


13 


4.18 


50 


15.93 


87 


27.7 


124 


39.47 


161 


51.25 


14 


4.49 


51 


16.24 


88 


28.02 


125 


39.79 


162 


51.57 


15 


4.81 


.52 


16.56 


89 


28.33 


126 


40.11 


163 


51.89 


16 


5.12 


53 


16.88 


SO 


28. C5 


127 


40.43 


164 


52.21 


17 


5.44 


54 


17.2 


91 


28.97 


128 


40.75 


165 


52.52 


18 


5.76 


55 


17.52 


92 


29.29 


129 


41.07 


166 


52.84 


19 


6.07 


56 


17.8 


93 


29.61 


130 


41.38 


167 


53.16 


20 


6.39 


57 


18.15 


94 


29.93 


131 


41.7 


168 


53.48 


21 


6.71 


58 


18.47 


95 


30.24 


132 


42.02 


169 


53.8 


22 


7.03 


59 


18.79 


9H 


30.56 


133 


42.34 


170 


54.12 


23 


7.34 


60 


19.11 


97 


30.88 


134 


42.66 


171 


54.43 


24 


7.66 


61 


19.42 


98 


31.2 


135 


42.98 


172 


54.75 


25 


7.98 


62 


19.74 


99 


31.52 


136 


43.29 


173 


55.07 


26 


8.3 


63 


20.06 


100 


31.84 


137 


43.61 


174 


55.39 


27 


8.61 


64 


20.38 


101 


32.15 


138 


43.93 


175 


55.71 


28 


8.93 


65 


20.7 


102 


32.47 


139 


44.25 


176 


56.02 


29 


9.25 


66 


21.02 


103 


32.79 


140 


44.57 


177 


56.34 


30 


9.57 


67 


21.33 


104 


33.11 


141 


44.88 


178 


56.66 


31 


9.88 


68 


21.65 


105 


33.43 


142 


45.2 


179 


56.98 


32 


10.2 


69 


21.97 


106 


33.74 


143 


45.52 


180 


57.23 


33 


10.52 


70 


22.29 


107 


34.06 


144 


45.84 


181 


57.62 


34 


10 = 84 


71 


22.61 


108 


34.38 


145 


46.16 


182 


57.93 


35 


11.16 


72 


22.92 


109 


34.7 


146 


- 46.48 


183 


58.25 


36 


11.47 


73 


23.24 


110 


35.02 


147 


46.79 


184 


58.57. 


37 


11.79 


74 


23.56 


111 


35.34 


148 


47.11 


185 


58.89 


38 ' 


12.11 


75 


23.88 


112 


35.65 


149 


47.43 


186 


59.21 


39 


12.43 


76 


24.2 


113 


35.97 


150 


47.75 


187 


59.53 


40 


12.74 


77 


24.52 


114 


36.29 


151 


48.07 


188 


59.84 


41 


13.06 


78 


24.83 


115 


36.61 


152 


48.39 


189 


60.16 


42 


13.38 


79 


25.15 


116 


36.93 


153 


48.7 


190 


60.48 


43 


13.7 


80 


25.47 


117 


37.25 


154 


49.02 


191 


60.81 


44 


14.02 


81 


25.79 


118 


37.56 


155 


49.34 


192 


61.13 



HANDBOOK ON ENGINEERING. 



705 



TO COMPUTE THE STRESS THAT MAY BE BORNE BY A TOOTH. 

Rule* — Multiply the value of the material of the tooth to re- 
sist transverse strain, as estimated for this character of stress, by 
the breadth and square of its depth, and divide the product by 
the extreme length of it in the decimal of a foot. 

TO COMPUTE THE NUMBER OF TEETH OF A WHEEL FOR A GTVEN 
DIAMETER AND PITCH. 

Rule* — Divide the diameter by the pitch, and opposite to the 
quotient in the preceding table is given the number of teeth. 

TEETH OF WHEELS. 

Epicycloid al* — In order that the teeth of the wheels and pin- 
ions should work evenly and without unnecessary rubbing fric- 
tion, the face (from pitch line to top) of the outline should be 
determined by an epicycloidal curve, and the flank (from pitch 
line to base) by an hypocycloidal. When the generating circle is 
equal to half the diameter of the pitch circle, the hypocycloid de- 
scribed by it is a straight diametrical line, and consequently the 
outline of a flank is a right line and radial to the center of the 
wheel. If a like generating circle is used to describe face of a 
tooth of other wheel or pinion respectively, the wheel and pinion 
will operate evenly. 

Involute* — Teeth of two wheels will work truly together when 
surfaces of their face is an involute ; and that two such wheels 
should work truly, the circles frOm which the involute lines for 
each wheel are generated must be concentric with the wheels, 
with diameters in the same ratio as those of the wheels. 

Curves of teeth* — In the pattern shop, the curves of epicy- 
cloidal or involute teeth are defined by rolling a template of the 
generating circle on a template corresponding to the pitch line, 
a scriber on the periphery of the template, being used to define 

45 



706 



HANDBOOK ON ENGINEERING. 



the curve. Least number of teeth that can be employed in pin- 
ions having teeth of following classes, are : involute, 25 ; 
epicycloidal, 12 ; staves or pins, 6. 



CONSTRUCTION OF GEARING. 

If the dimensions of two wheels are determined, as well as 
the size of the teeth and spaces, the wheel is drawn as shown 
in figure. The starting- 
point for the division of 
the wheels is where the 
two pitch circles meet 
in i. It is advisable 
to determine the exact 
diameters of the wheels 
by calculation, if the 
difference between 
them is remarkable ; for 
any division upon two 
circles of unequal size 
by means of a divider, 
is incorrect, because the latter measures the chord instead of the 
arc. From the point A we construct the epicycloid C, by rolling 
the circle A upon B, as its base line. That short piece of the epi- 
cycloid, from the pitch line to the face of the tooth, is the curva- 
ture for that part of the tooth and the wheel B. This curvature 
obtained for one side of the tooth, serves for both sides of it, and 
also for all the teeth in the wheel. The lower part of the tooth, 
or that inside the pitch-line, is immaterial to the working of the 
wheel ; this may be a straight line, as shown by the dotted lines 
which are in the direction of the diameters, or may be a curved 
line, as is seen in the wheel A. This line must be so formed as 
not to touch the upper or curved part of the tooth. The root of 




HANDBOOK ON ENGINEERING. 



707 



the tooth, or that part of it which is connected with the rirn of the 
wheel, is the weakest part of the tooth, and may be strengthened 
by filling the angles at the corners. The curvature for the teeth 
in the wheel A is found in a similar manner to that of B. The 
pitch circle A serves now as a base line, and the circle B is rolled 
upon it, to obtain the circle D. This line forms the curvature for 
the teeth of A, and serves for all the teeth in A — also for both 
sides of the teeth. In most practical cases the curvature of the 
teeth is described as a part of a circle, drawn from the center of 
the next tooth, or from a point more or less above or below that 
center, or the radius greater or less in strength than the pitch of 
the wheel. Such circles are never correct curves, and no rule can 
be established by which their size and center meets the form of 
the epicycloid. 

BEVEL WHEELS. 

If the hues C A and B C represent the prolonged axes, which 
are to revolve with different or similar velocities, the position and 

sizes of the wheels for 
driving these axes are 
determined by the dis- 
tance of the wheels from 
the point C. The diame- 
ters of the wheels are as 
the angles a and b and 
inversely as the number 
of revolutions. These 
angles are, therefore, to 
be determined before the 
wheels can be drawn. 
By measuring the distances from C to the line E, or from C to 
F, the sizes of the wheels are determined. These lines E, F and 
D F, are the diameters for the pitch lines ; from th'em the form 




708 



HANDBOOK ON ENGINEERING. 



of the tooth is described on the beveled face of the wheel. If 
the form of the tooth is described on the largest circle of the 
wheel, all the lines from this face run to the point O, so that when 
the wheel revolves around its axis, all the lines from the teeth 
concentrate in the point 0, and form a perfect cone. Curvature, 
thickness, length and spaces are here calculated as on face 
wheels ; the thickness is measured in the middle of the width of 
the wheel. 

WORM-SCREW. 

If a single screw A works in a toothed wheel, each revolution 
of the screw will turn the wheel one cog ; if the screw is formed 
of more than one thread, a corresponding number of teeth will be 
moved by each revolution. 
With the increase of the 
number of threads, the side 
motion of the wheel and 
screw is accelerated ; and 
when the threads and num- 
ber of teeth are equal, an 
angle of 45° is required for 
teeth and thread, provided 
their diameters also are 
equal. This motion causes 
a great deal of friction and 
it is only resorted to where no other means can be employed to 
produce the required motion. In small machinery, the worm is 
frequently made use of to produce a uniform, uninterrupted 
motion ; the screw, in such cases, is made of hardened steel and 
the teeth of the wheel are cut by the screw which is to work in 
the wheel. If the form of the teeth in the wheel is not curved 
and its face is concave so as to fit the thread in all points, the 
screw will touch the teeth but in one point and cause them to be 
liable to breakage. 




HANDBOOK ON ENGINEERING. 709 

PROPORTIONS OF TEETH OF WHEELS. 

Tooth* — In computing the dimensions of a tooth, it is to be 
considered as a beam fixed at one end, the weight suspended 
from the other, or face of the beam ; and it is essential to con- 
sider the element of velocity, as its stress in operation, at high 
velocity with irregular action, is increased thereby. The dimen- 
sions of a tooth should be much greater than is necessary to resist 
the direct stress upon it, as but one tooth is proportioned to bear 
the whole stress upon the wheel, although two or more are 
actually in contact at all times ; but this requirement is in 
consequence of the great wear to which a tooth is subjected 5 
the shocks it is liable to from lost motion when so worn as to 
reduce its depth and uniformity of bearing, and the risk of the 
breaking of a tooth from a defect. A tooth running at a low 
velocity may be materially reduced in its dimensions compared 
with one running at high velocity and with a like stress. The 
result of operations with toothed wheels, for a long period of 
time, has determined that a tooth with a pitch of 3 inches and a 
breadth 7.5 inches will transmit, at a velocity of 6.66 feet per 
second, the power of 59.16 horses. 

TO COMPUTE THE DEPTH OF A CAST-IRON TOOTH. 

1. When the stress is given. 

Rule* — Extract the square root of the stress, and multiply it 
by .02. 

Example. — The stress to be borne by a tooth is 4886 lbs. ; 
what should be its depth? 

l/4886x .02 = 1.4 in. 

2. When the horse-power is given. 

Rule* — Extract the square-root of the quotient of the horse- 
power divided by the velocity in feet per second, and multiply it 
by .466. 



710 HANDBOOK ON ENGINEERING. 

Example. — The horse-power to be transmitted by a tooth is 
60, and the velocity of it at its pitch-line is 6.66 feet per second ; 
what should be the depth of the tooth ? 
"60" 



i, 



-x.466 = 1.398 in. 



TO COMPUTE THE HORSE -POWER OF A TOOTH. 

Rule* — Multiply the pressure at the pitch-line by its velocity 
in feet per minute, and divide the product by 33,000. 

CALCULATING SPEED WHEN TIME IS NOT TAKEN INTO ACCOUNT. 

Rule* — Divide the greater diameter, or number of teeth, 
by the lesser diameter or number of teeth, and the quotient is 
the number of revolutions the lesser will make, for one of the 
greater. 

Example. — How many revolutions will a pinion of 20 teeth 
make, for 1 of a wheel with 125? 

125 divided by 20 == 6.25 or 6 J revolutions. 

To find the number of revolutions of the last to one of the first, 
in a train of wheels and pinions : — 

Rule* — Divide the product of all the teeth in the driving by 
the product of all the teeth in the driven ; and the quotient equals 
the ratio of velocity required. 

Example 1. — Required the ratio of velocity of the last, to 1 

of the first, in the following train of wheels and pinions, viz. : 

pinions driving — the first of which contains 10 teeth, the second 

15, and third 18. Wheels driven, first teeth 15, second 25, 

10x15x18 
and third 32. r^ — ^ — ^ = -225 of a revolution the wheel 

will make to one of the pinion. 

Example 2. — A wheel of 42 teeth giving motion to 1 of 12, 
on which shaft is a pulley of 21 inches diameter, driving 1 of 6 ; 



HANDBOOK ON ENGINEERING. 711 

required the number of revolutions of the last pulley to 1 of the 

42x21 

first wheel. 7^ »= 12.25 or 121 revolutions. 

12 x 6 4 

Note. — Where increase or decrease of velocity is required to 

be communicated by wheel- work, it has been demonstrated that 

the number of teeth on each pinion should not be less than 1 to 

6 of its wheel, unless there be some other important reason for a 

higher ratio. 

WHEN TIME MUST BE REGARDED. 

Rule* — Multiply the diameter or number of teeth in the driver 
by its velocity in any given time, and divide the product by the 
required velocity of the driven ; the quotient equals the number 
of teeth or diameter of the driven, to produce the velocity 
required. 

Example I . — If a wheel containing 84 teeth makes 20 revolu- 
tions per minute, how many must another contain, to work in 
contact, and make 60 revolutions in the same time: 
80 x 20 divided by 60 =27 teeth. 

Example 2. — From a shaft making 45 revolutions per minute 
and with a pinion 9 inches diameter at the pitch-line, I wish 
to transmit motion at 15 revolutions per minute ; what, at the 
pitch-line, must be the diameter of the wheel? 

45 x 9 divided by 15 = 27 inches. 

Example 3. — Required the diameter of a pulley to make 16 
revolutions in the same time as one of 24 inches making 36. 
24 x 36 divided by 16 = 54 inches. 

The distance between the centers, and the velocities of two wheels 
being given, to find their proper diameters : — 

Rule* — Divide the greatest velocity by the least ; the quo- 
tient is the ratio of diameter the wheels must bear to each other. 
Hence, divide the distance between the centers by the ratio -f- 1 ; 
the quotient equals the radius of the smaller wheel ; and subtract 



712 HANDBOOK ON ENGINEERING. 

the radius thus obtained from the distance between the centers ; 
the remainder equals the radius of the other. 

Example. — The distance of two shafts from center to center 
is 50 in. and the velocity of the one 25 revolutions per minute, 
the other is to make 80 at the same time ; the proper diameters 
of the wheels at the pitch line are required. 

80 divided by 25=3.2, ratio of velocity, and 50 divided b}- 
3.2-f- 1 == 11.9, the radius of the smaller wheel ; then 50 minus 
11.9 = 38.1, radius of larger ; their diameters are 11.9 x 2 = 23.8 
and 38.1x2 = 76.2 in. 

To obtain or diminish an accumulated velocity by means of 
wheels and pinions, or wheels, pinions and pulleys, it is necessary 
that a proportional ratio of volocity should exist, and which is 
thus attained ; multiply the given and. required velocities together ; 
and the square root of the product is the mean or proportionate 
velocity. 

Example. — Let the given velocity of a wheel containing 54 
teeth equal 16 revolutions per minute, and the given diameter of 
an intermediate pulley equal 25 in., to obtain a velocity of 81 
revolutions in a machine ; required the number of teeth in the 
intermediate wheel and diameter of the last pulley. 

V 81x16 =36 mean velocity; 54x16 divided by 36=24 
teeth, and 25x36 divided by 81 = 11.1 in., diameter of pulley. 

TABLE OF THE WEIGHT OF A SQUARE FOOT OF SHEET IKON IX 
FOUNDS AVOIRDUPOIS. 

No. 1 is T % of an inch ; No. 4, i ; No. 11, J, etc. 

No. on wire gauge, 1 2 3 45678 9 10 11 12 
Poundsavoir., 12.5 12 11 10 9 8 7.5 7 6 5.68 5 4.62 

No. on wire gauge, 13 14 15 16 17 18 19 20 21 22 
Poundsavoir., 4.31 4 3.95 3 2.5 2.18 1.93 1.62 1.5 1.37 



HANDBOOK ON ENGINEERING. 713 

SCREW-CUTTING. 

In a lathe properly adapted, screws to any degree of pitch, or 
number of threads in a given length, may be cat by means of a 
leading screw of any given pitch, accompanied with change wheels 
and pinions ; coarse pitches being effected generally by means of 
one wheel and one pinion with a carrier, or intermediate wheel, 
which cause no variation or change of motion to take place ; hence, 
the following : — 

Rule* — Divide the number of threads in a given length of the 
screw which is to be cut, by the number of threads in the same 
length of the leading screw attached to the lathe, and the quotient 
is the ratio that the wheel on the end of the screw must bear to 
that on the end of the lathe spindle. 

Example. — Let it be required to cut a screw with 5 threads 
in an inch, the leading screw being of i inch pitch, or containing 
2 threads in an inch ; what must be the ratio of wheels applied? 

5 divided by 2 = 2.5, the ratio they must bear to each other. 
Then suppose a pinion of 40 teeth be fixed upon for the spindle ; 
40 x 2.5 = 100 teeth for the wheel on the end of the screw. 

But screws of a greater degree of fineness than about 8 threads 
in an inch are more conveniently cut by an additional wheel and 
pinion, because of the proper degree of velocity being more 
effectively attained, and these, on account of revolving upon a 
stud, are commonly designated the stud- wheels, or stud-wheel 
and pinion ; but the mode of calculation and ratio of screw are the 
same as in the preceding rule. Hence, all that is further neces- 
sary is to fix upon any three wheels at pleasure, as those for the 
spindle and stud-wheels ; then multiply the number of teeth in 
the spindle-wheel by the ratio of the screw and by the number of 
teeth in that wheel or pinion which is in contact with the wheel 
on the end of the screw ; divide the product by the stud-wheel in 
contact with the spindle- wheel, and the quotient is the number of 
teeth required in the wheel on the end of the leading screw. 



714 



HANDBOOK ON ENGINEERING. 



Example. — Suppose a screw is required to be cut containing 

25 threads in an inch, and the leading screw, as before, having 

two threads in an inch, and that a wheel of 60 teeth is fixed upon 

for the end of the spindle, 20 for the pinion in contact with the 

screw-wheel, and 100 for that in contact with the wheel on the 

end of the spindle ; required the number of teeth in the wheel for 

the end of the leading screw. 

oeT -j t l o io k , 60s 12.5 x 20 

25 divided by 2 = 12.5, and __ _- 150 teeth. 

Or suppose the spindle and screw wheels to be those fixed upon, 
also any one of the stud-wheels, to find the number of teeth in the 
other. 



150 x 100 
60x12.5 



= 20 teeth, or 



60 x 12.5 x 20 



150 



= 100 teeth. 



Transmission of Power by Manilla Rope, 
power Transmitted. 



Horse- 



Feet per minute .... 


1000 


1500 


2000 


2500 


3000 


3500 


4000 


4500 


5000 


Diameter of Rope . 


. % 


U 


21 


3* 


4* 


5* 


6* 


7 


8 


9 


a u 


. 1 


H 


4ft 


64 


8 


10 


11 


13 


15 


16 


<( (i 


. u 


5* 


n, 


10i 


13 


15 


18 


20 


23 


26 


a it 


. H 


7* 


ii 


15 


18 


22 


26 


30 


34 


37 


u << 


. 11 


10 


15 


20 


25 


30 


35 


40 


45 


50 


u u 


. 2 


13 


194 ^6 


33 


39 


46 


52 


59 


65 



Decimal Equivalents of One Foot by Inches. 



k 


h 


1 


1 


2 


0208 


.0417 


.0626 


.0833 


.1667 


6 


7 


8 


9 


10 


5000 


.5833 


.6667 


.7510 


.8333 




HANDBOOK ON ENC4INEERING. 



715 



TABLE OF TRANSMISSION OF POWER BY 
WIRE ROPES. 

This table is based upon scientific calculations, careful observations 
and experience, and can be relied upon when the distance exceeds 100 
feet. We also find by experience that it is best to run the Wire Rope 
Transmission at the medium number of revolutions indicated in the table, 
as it makes the best and smoothest running transmission. If more 
power is needed than is indicated at 80 to 100 revolutions, choose a 
larger diameter of sheave. 





GO 






o 


o 


J_, 




a» 


s 


£> 




s 


o 
> 


s 




£P5 



3 
3 

3 
3 
4 


80 
100 
120 
140 

80 


4 


100 


4 


120 


4 


140 


5 


30 


5 


100 


5 


120 


5 


140 


6 


80 


6 


100 


6 


120 


6 


140 


7 


80 


7 


100 


7 


120 



2& 



A 
A 
A 
A 
h 
h 



<W • 




«M 


u a 


o§ 


o 

Si . 


a> -^ 




CD Q> 


«3 <D 


11 


II 




3 © 




Qcc 


&P3 


3 



3 

3£ 

4 

4 

4 
5 

6 

7 

9 

11 

13 

15 

14 

17 

20 

23 
20 
25 



7 
8 
8 
8 
8 


140 
80 
100 
120 
140 


A 
1 
ft 

1 
1 


9 


80 


{A* 


9 


100 


^16 8 


9 


120 


{A ft 


9 


140 


{A,.! 


10 


80 


H 16 


10 


100 


{hi 


10 


120 


{ft H 


10 


140 


{ft \\ 


12 


80 


{ttl 


12 


100 


{hi 


12 


120 


{fil 


12 


120 


1 


14 


80 


{l H 


14 


100 


{i U 



716 HANDBOOK ON ENGINEERING. 



CHAPTER XXV. 
ELECTRIC ELEVATORS. 

In factories, warehouses and business buildings, freight, and in 
some instances passenger elevators, are operated by machines 
that are arranged to be driven by a belt. Such machines are 
variously called belted elevators, factory elevators and sometimes 
warehouse elevators. 

In factories where there is a line of shafting kept running 
continuously,. they are driven from it. As a rule the elevator 
machine is driven from a countershaft which latter is belted to 
the line shaft. Very often the elevator machine is driven 
directly from the line shaft. As the line shaft runs always in the 
same direction, the only way in which the elevator machine can 
be made to run in both directions is by the use of two belts, one 
open and the other crossed, or some form of gearing that will 
accomplish the same result. The common practice is to use 
double belts. Either one of these belts can be made to drive by 
using friction clutches, or by having tight and loose pulleys, and 
a belt shifter. The latter arrangement is the most common. 

In buildings where there is no line of shafting, power for oper- 
ating the elevator machine must be derived from some kind of 
motor installed expressly for the purpose. Nowadays electric 
motors are very extensively used for this purpose, and the com- 
bination of an elevator machine and an electric motor to drive it is 
very generally called an electric elevator, although in reality it is not 
such, but simply a belted elevator machine driven by an electric 
motor. It has become so common, however, to call such com- 
binations electric elevators, that true electric elevators are generally 
designated as " direct connected electric elevators." 



HANDBOOK ON ENGINEERING. 717 

The first impression would be that in the combination of a 
belted elevator machine, and an electric motor to drive it, as the 
motor simply furnishes the power to set the machine in motion, 
there can be nothing about the combination that requires any 
special elucidation. Such a conclusion, however, would not be 
correct, for there are several ways in which the combination can 
be arranged, and in what follows I propose to explain these 
several combinations, pointing out the important features of 
each. 

The simplest way in which a motor can be installed to drive 
an elevator, is to arrange it so as to drive the counter shaft con- 
tinuously, in which case the elevator is stopped and started by 
throwing the belts on the tight or the- loose pulley. Although 
this is a very simple arrangement, it is not desirable unless the 
elevator is kept in service all the time. In buildings where the 
elevator is used only at intervals, a great amount of power is 
wasted if the shafting is kept running all the time ; hence it is 
desirable to arrange the motor so that it can be stopped when the 
elevator is stopped, and started whenever the elevator is to be 
used. 

If the motor is arranged so as to run all the time, it is provided 
with a simple motor-starting switch, the same as is used for any 
motor installed to operate machinery of any kind. If the motor 
is started and stopped whenever the elevator is started and stopped, 
it is necessary to provide a motor-starter that can be operated 
from the elevator car. A very common way of arranging a motor 
to start and stop with the elevator is illustrated in the diagram 
(Fig. 1). 

In this diagram the elevator car is shown at (7, with the lifting 
ropes running over the sheave F at the top of the elevator 
shaft, and then down and around the drum A of the elevator 
machine. This drum is driven by means of screw gearing, as a 
rule, with driving pulleys on the screw shaft as shown at B The 



718 



HANDBOOK ON ENGINEERING. 



driving motor is shown at 31, and the counter-shaft to which it is 
belted is at D. In this arrangement the elevator machine is pro- 
vided with a tight center pulley and loose pulleys on the two sides, 
The belts are shown on the loose pulleys, one being open and the 




other being crossed . The countershaft carries a drum wide 
enough to allow for the side movement of the belts when one or 
the other is shifted upon the tight center pulley by the belt shifter 
s. To operate the elevator car, a hand rope is provided which 



HANDBOOK ON ENGINEERING. 719 

runs up the elevator shaft at one side of the car from bottom to 
top of building. This rope is shown in the diagram at I, and 
runs around two small sheaves a a. The lower one of these sheaves 
is provided with a crank pin which moves the connecting rod 6, 
and thus rocks the lever r, and thereby moves the belt shifter s. 
To cause the car to ascend the hand rope I is pulled down, and 
to make the car descend, the hand rope is pulled up. As will be 
seen from this explanation, the lower sheave a will rotate in one 
direction when the hand rope is pulled to make the car go up, and 
in the opposite direction when the rope is pulled to make the car 
run down. In the diagram, sheave a is shown in the stop posi- 
tion, therefore when the hand rope is pulled down so as to make 
the car run up, the sheave will turn in a direction opposite to the 
movement of the hands of a clock, and thus the belt shifter will 
be moved to the right, audthe open belt will be run onto the tight 
center pulley. If the hand rope is pulled up sheave a will rotate 
in the direction of the hands of a clock, and the belt shifter will 
move toward the left and thus shift the crossed belt onto the tight 
pulley. The rope p is a stop rope and is connected with the two 
sides of the hand rope in the manner shown, so that when the car 
is running in either direction, if p is pulled hard it will bring I to 
the position shown in the diagram, and thus stop the car. This 
rope can be dispensed with, but the objection is that in pulling 
the hand rope I to stop the car it may be pulled too far and then 
the car will not only be stopped but it will be caused to run in 
the opposite direction. 

The motor starting switch is shown at E, the line wires being 
connected with the two top binding posts. The lever c c is in one 
piece and is independent of lever e, but both swing around the 
same pivot. At m, a dash pot is provided which acts to prevent 
the too rapid movement of lever e. As will be noticed, lever c 
has a projection which holds lever e up. The operation of this 
motor starter is as follows : When the hand rope I is pulled in 



720 HANDBOOK ON ENGINEERING. 

either direction, the rope h draws lever c towards the left and 
causes it to make contact with the switch jaw j. In this way the 
current from the upper binding post which is connected with j 
through wire #, passes to lever e, and thus to the starting resist- 
ance, which is indicated by the dotted lines t, to binding post ft, 
from where it goes to the motor armature through wire d., and re- 
turns through the other wire d to the upper binding post at the 
right side, which is connected with the opposite side of the main 
line, thus completing the circuit. The field current branches off 
from the upper end of the starting resistance i and reaches the 
field coils through wire/, and through the lower wire / reaches 
the return armature wire d and thus the opposite side of the cir- 
cuit. When the rope h pulls lever c over toward the left, the lever 
e does not follow it, as it is held up by the dash pot m. The 
weight on the end of e gradually overcomes the resistance of the 
dash pot, and thus causes lever e to move downward slowly. The 
velocity at which e moves downward is graduated by adjusting 
the opening in the dash pot through which the oil flows. 

From the foregoing it will be seen that the starter E is made so 
as to accomplish automatically just what a man accomplishes 
when he moves the lever of an ordinary motor-starter ; that is, it 
first closes the circuit through the motor, by bringing lever c into 
contact with/; and then allows lever e to move slowly so as 
to cut the resistance i out of the armature circuit gradually. 
When the elevator is stopped, by pulling the hand rope I to the 
stop position, the rope h slacks up and then the weight on the end 
of lever c causes it to descend, and thus return lever e to the posi- 
tion shown in the diagram, and also to break the circuit between 
c and j. 

The elevator machine A is provided with a brake which is 
actuated by the belt shifter s, so that when the belts are shifted 
upon the side pulleys, as shown in the diagram, the brake is put 
on, and thus the machine is stopped. As soon as the belt shifter 



HANDBOOK ON ENGINEERING. 721 

is moved to set the car in motion the brake is raised, so as to 
allow the machine to run free. 

This arrangement is used very extensively, although the motor- 
starting switch is not always made in strict accordance with the 
one shown at E. In fact, there are a great many different designs 
on the market, but they all accomplish the same result, although 
the means employed may be very different. 

Although it is very advantageous to have the motor arranged 
as in Fig. 1, so that it may be stopped and started together with 
the elevator, there is one objection to it which is sometimes re- 
garded as serious, and that is, that as it requires a great amount 
of power to start an elevator from a state of rest, the motor will 
take a very strong current in the act of starting. To get around 
this objection, it is a common practice to provide a separate rope 
for starting the motor, and then when it is desired to use the ele- 
vator, the motor rope is pulled first, and in half a minute or so, 
the main hand rope is pulled. In this way the motor gets a start 
ahead of the elevator, and the headway of the motor armature 
helps to set the elevator car in motion, so that the current taken 
by the motor to start the elevator is very much reduced. 

When a separate rope is used to start the motor,in advance of 
the elevator, the starter E, or the levers connecting with it, are 
made so that while the motor can be started independently of the 
elevator car, when the main hand rope is pulled to stop the car, 
it also stops the motor. If this arrangement were not provided, 
the operator might stop the elevator and forget to stop the motor, 
in which case the latter would keep on running and waste power. 

The main hand rope I is provided with stops at top and 
bottom of the elevator shaft, so that the car may be stopped auto- 
matically should the operator forget to pull the hand rope at the 
proper time. 

It is the universal practice with elevator machines of the type 
shown in Fig. 1 to counterbalance the elevator car, but I have 
not shown a counterbalance in this diagram as it would only serve 



722 



HANDBOOK OX ENGINEERING. 



to complicate its appearance, and it is not necessary to show it as 
the electrical features will be the same whether there is a counter- 
balance or not. This diagram also shows a separate rope I for 
actuating the starter E, but in actual machines E is generally 




CONTROLLER 



ELLEVA TOR 



DIAGRAM SHOWING CONNECTIONS 
GRAVITY MOTOR CONTROLLER 
ELEVATOR 



#% *. 




operated from the lower sheave a, which also actuates the belt 
shifter. 

Fig, 2 is a diagram that shows the way in which one of the 
various motor starters in actual use is connected with the motor 






HANDBOOK ON ENGINEERING. 



723 



and the operating hand rope. In this illustration A is the lower 
sheave a of Fig. 1, and F represents the hoisting drum and E the 
driving pulleys of the elevator machine, G being the lifting ropes 
from which the car is suspended. The sheave A is rotated 

1 ^///////////////////////////////////////A r 




DIAGRAM OF CONNECTIONS OF A 



K -H 



GRAVITY MOTOR CONTROLLER. 
WTH SEPERATE ROPE ATT A CHMENT 



£^ta .3 




through one quarter of a turn in either direction by the pull on 
the hand rope B, and when so rotated shifts the belt shifter and 
also lifts the brake from the brake- wheel. At the same time the 
crank pin C pulls up the connecting rod, and thus the upper end 



724 HANDBOOK ON ENGINEERING. 

of rod c, which takes the place of lever c in Fig. 1. In this 
way the switch blades in the lower end of c are raised into con- 
tact with the clips jj, which take the place of contact j in Fig. 1, 
and thus the circuit is closed. A projection s on c holds the 
switch e in the upper position, but when c is raised, s goes up with 
it, and then e is free to descend by the force of gravity acting 
upon the weight w. The dash pot m is set so as to retard the 
movement of e as much as may be desired. The outer end of e 
glides over the contacts i in its downward movement, and thus 
cuts out of the armature circuit the starting resistance. This 
resistance is contained in the controller box. 

Fig* 3 shows the same type of controller as in Fig. 2, but it is 
arranged so that the motor may be started ahead of the elevator. 
The separate motor-starting rope is shown at H. When this rope 
is pulled, it elongates the spiral spring A" which is connected with 
the stud G fixed in the upper end of rod c. The rope H is pulled 
up enough to stretch K until the lever D is lifted, II being attached 
to its outer end I. When I) is lifted sufficiently, its inner end dis- 
engages the stud 6r, and allows it to slide upward in the slot 
shown in dotted lines, in the lower end of the connecting rod. 
In this way the motor is started ahead of the elevator machine. 
If now the elevator machine is started, by pulling on the main 
hand rope FF, the crank pin C on the hand rope sheave will lift 
the connecting rod C, and when it reaches its upper position, the 
catch-lever D will drop into the position shown in the illustration, 
and thus lock the stud G, so that when the elevator is stopped, 
the rotation of the hand rope sheave will push rod C downward 
and thus stop the motor, as well as shift the belts and stop the 
elevator machine. 

In the three illustrations shown the motor is run always in the 
same direction and the reversing of the direction of rotation of 
the hoisting drum is effected by the use of double belts and a 
belt shifter, or friction clutches which cause one or the other of 



HANDBOOK ON ENGINEERING. 725 

the belts to do the driving. The way in which machines of this 




type are installed can be more folly understood from Fig. 4. 



726 HANDBOOK ON ENGINEERING. 

This figure shows the position of the motor, the countershaft 
and the elevator machine with reference to the elevator shaft. 
This illustration is so clear that an explanation of it would be 
superfluous. 

In relation to the installation of elevator plants of this type 
all that need be said is that the motor must be of the shunt 
type, the same as those used for driving machines of any kind. 
A series wound motor, such as are used for electric railway 
cars, must not be used. Shunt wound motors cannot run above a 
certain speed, unless forced to do so by power applied from an 
external source, and in such an event they become generators of 
electricity and thus resist rotation. On this account, when they 
are used for elevator service, they not only move the elevator car, 
but when the latter is descending under the influence of a heavy load 
and tends to run away, the motor at once begins to act as a gen- 
erator, and is thus converted into a brake which holds the car and 
prevents it from attaining a speed much above the normal ; in 
fact, the difference between the car velocity when lifting a heavy 
load, and when running down under the influence of a similar load 
is hardly enough to be noticed by any one not familiar with the 
elevator. 

The motor in these combinations is to be given the same care 
as those used for other purposes ; that is, it must be kept clean 
and the brushes properly set so as to run with as little spark as 
is possible. The controller switch requires more attention than the 
motor starters used with stationary motors, for the simple reason 
that it is used to a much greater extent. Every time the elevator 
is started or stopped the controller switch is actuated, hence, the 
switch levers are subjected to a considerable amount of wear, and 
the contacts are liable to become rough, either by cutting or by 
being burned on account of making imperfect contact. On this 
account the contact must be well examined at least once every 
day, and if burned or rough must be smoothed up. It is also 



HANDBOOK ON ENGINEERING. 



727 



necessary to see that all parts of the controller are properly se- 
cured, that none of the screws or pins are working out, and that 
the contacts and switch levers are not out of their normal posi- 
tion. 




As electric .motors can be run as well in one direction as the 
other, and as all that is required to make any motor reversible is 
to provide a reversing switch, it can be seen at once that by mak- 
ing use of such a switch, the direction of movement of the ele- 



728 HANDBOOK ON ENGINEERING. 

vator car can be reversed by simply reversing the motor, and thus 
do away with the complication of a countershaft and tight and 
loose pulleys. Owing to this fact elevator machines are now 
made so as to be used with reversing motors. These are usually 
called single-belt machines. The way in which such machines 
are connected with the motor and the type of controller required 
can be under stoood from the diagram Fig. 5. 

As will be seen, the principal difference in the machine itself 
is that the tight and loose pulleys are replaced by a single tight 
pulley which is only wide enough to carry the driving belt. 
Usually an extra pulley is provided for the brake, and this brake 
is mechanically operated in the same manner as upon machines 
provided with shifting belts. Another modification which is 
sometimes used, but is not shown in the diagram, is the arrange- 
ment of a brake so that same is operated by a magnet 
instead of by mechanical means. With this arrangement the 
magnet is arranged so that when the machine is in motion, the 
current passing through the magnet coil acts to lift the brake, 
and when the machine stops, the magnet lets go, and the brake 
goes on. By arranging the brake in this way it becomes perfectly 
safe ; for if the brake magnet fails to act, the brake will not be 
raised, and the machine will not move; that is, failure of the 
device to work properly will not permit the elevator car to move, 
thus calling attention to the fact that something is out of order. 

The operation of the reversing controller is as follows : the 
current from the line wires passes along the dotted connections 
h h to the contact i,i, i,i. The upper left hand i contact is con- 
nected with the lower right hand one, and the upper right hand 
with the lower left hand. The switch lever c is connected with 
lever e by means of the two springs r r, so that c may be moved 
either up or down without carrying e with it. The curved con- 
tact o is connected with j and the stud around which c and e 
swing is connected with ft, while g is connected with the ends of 



HANDBOOK ON ENGINEERING. 729 

the starting resistance n n by means of the wire /and the two 
wires s s. If the hand rope I is pulled so as to carry lever c 
upward, the current from the left side line wire will pass through 
upper left side i contact, to o, and thence to j and through wire b 
to the motor armature and returning through the other b wire will 
reach g and thenpass through / and lower s to lower end of n and 
thence to lever e and the inner end of lever c, which will be rest- 
ing on the upper right side i contact, thus reaching the right side 
line wire. The current for the field magnet coils will be drawn 
from j through wire d and back to k through the other wire d. 
As lever c has been moved upward, the upper spring r will be 
compressed, and the lower one will be stretched, hence a force 
will be exerted to move e downward over the lower contacts n and 
thus cut out the' starting resistance. As in the case of the con- 
troller in Fig. 1 the dash pot m by its resistance retards the move- 
ments of e, so as to cut out the resistance as gradually as may be 
desired. 

In the chapter on stationary motors it is shown that to prevent 
destructive sparking, when the starting switch is opened, the 
armature and field coils are connected so as to form a permanently 
closed loop. This style of connection is used in the non-revers- 
ing controller of Fig. 1, but it cannot be employed with a revers- 
ing controller, because both ends of the armature circuit must be 
free, so that they may be reversed when the direction of rotation 
is reversed. As this connection cannot be made, a very common 
expedient resorted to to prevent serious sparking when the switch 
is opened is to connect a string of incandescent lamps across the 
terminals of the field circuit, as is indicated at v v v. These 
lamps, together with the field coils, form a closed circuit, so that 
when the switch is opened, the field can discharge through the 
lamps, and thus avoid sparking at the controller contacts. The 
only objection to this arangement is that all the current that 
passes through the lamps is wasted, but by placing two or three 



730 HANDBOOK ON ENGINEERING. 

in series the loss is reduced to an insignificant amount. Another 
way in which the sparking is subdued, but only to a slight ex- 
tent, is by connecting the brake magnet coil with the binding 
posts j and k, which is the simplest and most generally used con- 
nection. The brake magnet coil together with the field coils form 
a closed loop when connected with J and k, but when the main cir- 
cuit is opened, the currents flowing in the two coils meet each other 
at j and k flowing in opposite directions, hence they both follow 
along the main circuit and try to jump across the gaps at the 
switch, and thus produce about as much sparking as if they were 
connected independently of each other. In tracing out the path 
of the current when lever c is moved upward, it was shown that the 
left side line went directly to the upper commutator brush. Now 
when c is moved downward, this same line wire runs to the lower 
commutator brush since the connections between the two upper 
i contacts and the two lower ones are crossed. To reverse the 
direction of rotation of a motor all that is required is to reverse 
the direction of the current through the armature, that through 
the field remaining unchanged, hence it will be seen that by cross- 
ing the connections between the upper and lower i contacts, the 
direction of rotation of the motor is reversed when the c lever is 
moved in opposite directions. 

DIRECT CONNECTED ELECTRIC ELEVATORS. 

The machines explained in the foregoing pages are simply 
combinations of an electric motor and a belt driven electric ma- 
chine, but, as already stated, they are commonly spoken of as 
" electric elevators." In what follows it is proposed to explain 
the construction and operation of true electric elevators, which 
are called " direct connected machines " to distinguish them from 
the combinations so far described. 

There are many designs of direct connected electric elevators 



HANDBOOK ON ENGINEERING. 



731 



now upon the market, and it would be out of the question to un- 
dertake to describe all of them in the space that can be devoted 
to the subject in this book. On that account the discussion will 
be confined to the designs that are most extensively used. The 
explanations here given, however, will be sufficient to enable any 




Fig. 6. 



one to understand the operation of any of the machines not de- 
scribed because the difference in the principle of operation is 
only slight. 



732 HANDBOOK ON ENGINEERING. 

Perhaps the type of direct connected electric elevator that 
is most extensively used is the Otis drum elevator with hand 
rope control which is illustrated in Fig. 6. This machine has 
been upon the market for twelve years or more, and is stili one of 
the standard Otis machines. It is called a hand rope control 
machine because the starting and stopping is controlled by the 
movement of a hand rope that passes through the elevator car. 
In the illustration, the sheave around which the hand rope passes 
can be seen located on the front end of the drum shaft. In a 
modification of the design, this sheave is mounted upon a sep- 
erate shaft but the way in which it acts is the same as in the pres- 
ent design. When the hand rope is pulled the sheave is 
rotated and the horizontal bar, running 'from it to the 
controller box, which is mounted on top of the motor » 
shifts the starting switch so as to run the machine in 
the direction desired. At the same time, the vertical lever ex- 
tending upward from the side of the brake wheel, lifts the brake 
and thus frees the motor shaft so that it may revolve unobstructed. 
The motor carries a worm on the end of the armature shaft which 
gears into the under side of a worm wheel mounted upon the 
drum shaft. This worm wheel runs in a casing seen just back of 
the hand rope sheave wheel. The sheave mounted upon the shaft 
directly above the drum is for the purpose of guiding the coun- 
terbalance ropes which run up from the back of the drum. In 
some buildings these ropes can be run up straight from the back 
of the drum, but in most cases they must run up in the elevator 
shaft in the space between the car and the side of the shaft. As 
these ropes wind upon the drum from one side to the other, the 
guiding sheave must move endwise on the shaft, hence it is called 
a traveling, or vibrating sheave. The levers seen projecting to 
the right of the machine from a small shaft just above the drum 
are what is called a slack cable stop, and their office is to stop 
the machine if the lifting cable becomes slack through the wedg- 



HANDBOOK ON ENGINEERING. 733 

ing of the car in the elevator shaft or any other cause. These 
levers are held in the position shown when the lifting ropes are 
tight, but drop out of position if the rope slackens up, and in 
dropping they release a lever which holds the weight seen under 
the hand rope sheave. The movement of this lever operates a 
catch that engages with the hand rope sheave and thus the hori- 
zontal bar that operates the brake and the controller switch is 
brought to the stop position and the rotation of the hoisting drum 
is stopped. 

The hand rope has fastened to it at the top and bottom of the 
elevator shaft stops that are moved by the car when it reaches 
either end of its travel, and thus the elevator machine is stopped 
automatically. This arrangement is the same as that used with 
the belt driven machines already described, but as an additional 
safety, a stop motion is provided on the machine itself, so that if 
the stops on the hand rope become displaced, the car will still be 
stopped automatically at the top and bottom landings. This stop 
motion is seen on the end of the shaft, just in front of the hand 
rope sheave, and consists of a nut that travels on the shaft as the 
latter revolves. At both sides of the screw there are projection 
cases upon the inclosing frame, which are struck by the traveling 
nut when it come3 near enough to either end. When the nut 
strikes the projection, the hand rope sheave is revolved with the 
shaft and thus the machine is stopped. To understand this ac- 
tion it must be remembered that the hand rope sheave does not 
revolve except when turned by the pull on the hand rope or by 
the action of the slack cable stop or the traveling nut. 

The controller box on top of the motor contains the starting 
resistance, the starting and reversing switch, and also a magnet 
to actuate a switch that gradually cuts out the starting resistance. 
The way in which the switches act to start and stop the motor 
can be readily explained by the aid of the diagram Fig. 7. 

This shows the circuit connections in the simplest possible 



734 HANDBOOK ON ENGINEERING. 

form. In this diagram all the wires whose presence would make 




M [ POTENTIAL SWTCH 



RESISTANCE INBOX 



^ 

4 

^ 

J. 

a_ 




ARM&PURE 

~\miimmmf 

SHUNT FIELD 



SAFETY MAGNET FOR 
BRAKE ON MACHINE 



c/vy X. 



the drawing confusing have been removed, but the manner w 



HANDBOOK ON ENGINEERING. 735 

which they are connected will be readily understood from the 
following explanation : — 

The main switch, which connects the motor circuits with the 
line, is located at the upper left hand corner of the diagram, the 
main line wires being marke -j- and — . When this switch is 
closed, the motor circuits are connected with the line, but the 
motor circuit itself is not closed so long as the switch M remains 
in the position shown. When this switch is turned about one 
quarter of a revolution in either direction, one end will ride over 
the upper contact and the other one over the lower contact. 
The reversing drum and switch M are mounted on the same 
spindle and move together. They are located within the con- 
troller box, on top of the motor, and are moved by the horizontal 
bar ; see Fig. 6. The shaded portions of the drum, on which the 
brushes 7i and * rest are made of insulating material so that when 
switch M and the reversing drum are in the position shown the 
motor circuit is open at two points. This is the position of these 
parts when the machine is stopped. 

The starting resistance is shown above the reversing drum, 
and in the machine it occupies the space at the back of the con- 
troller box, shown on top of the motor in Fig. 6. The segment 
R is a series of contacts that are connected with the resist- 
ance in the resistance box; No. 2 contact being con- 
nected with point 2 on the resistance and so on for all the other 
numbers. The switch arm JVis moved over the contacts R by a 
magnet that is represented by the spiral L. The motor arma- 
ture and the shunt and series field coils are shown at the bottom 
of the diagram. The motor is compound wound, it being made 
so for the purpose of keeping the starting current as low as possi- 
ble. The path of the current through the wires is as follows : Sup- 
pose the reversing drum and the Jf switch are revolved in the direc- 
tion in which the hands of a clock move, then brushes g and i will 
rest on one segment, and h and k will rest on the other segment. 



736 HANDBOOK ON ENGINEERING. 

As switch M will now be closed, the current will flow to brush 
g and through the reversing drum segment to brush i; then it 
will follow the wire to the right side / of the armature and pass- 
ing through the latter will reach wire E and thus brush h, from 
which it will pass to brush k. From this brush the current will 
go to and through magnet L and by wire C ' and switch N will 
reach contact No. 10. As this contact is connected with point 
10 of the resistance the current will reach the latter and will pass 
through the whole of it, coming out at the opposite end G. This 
end is connected with contact (7, so that from this segment the 
current can flow through wire O to the end F of the series field 
coils, and passing through these to end II, will find its way to 
wire /, and thus return to the opposite side of the main line. 
From this explanation it will be seen that the current will pass 
through the motor armature, and then through the whole of the 
resistance in the resistance box, and then through the series field 
coils, and finally reach the other side of the main line. From 
the switch M another current will branch off and run to binding 
post D, and thence through the shunt field coil to binding post 
J^and thus to wire/, and through the latter to the opposite of 
the main line. 

The switch lever N is in some cases arranged so that the mag- 
net L acts to hold it upon contact 10 and a spring acts to carry 
it forward toward contact^.; in other cases the magnet is wound 
with two coils, one of which pulls N in one direction and the 
other pulls it in the opposite direction, the two coils being so pro- 
portioned that N moves gradually from contact 10 toward con- 
tact A. If we take the spring arrangement, then magnet L will 
pull N back toward contact 10, and the spring will pull it forward. 
As the starting current is very strong, ^will be held on contact 
10, but as the current weakens, the spring will begin to overpower 
the magnet, and .ft 7 " will slide over contact 9 and then 8 and 7 and 
so on to contact A. As contact 9 is connected with the point 9 



HANDBOOK ON ENGINEERING. 737 

of the resistance, when breaches it, the section of the resistance 
between points 10 and 9 will be cut out. When N reaches con- 
tact 7 the resistance between points 10 and 7 will be cut out for 
the latter point is connected with contact 7. As all the contacts 
are connected with the corresponding points of the resistance, 
when JV reaches contact C, all the resistance in the resistance box 
will be cut out of the circuit. As will be noticed, contact B is 
connected w T ith the center point G of the series field coil so that 
when JV reaches contact B one-half of the series coils will be cut 
out in addition to the whole of the resistance box. When N 
reaches contact A the current will pass directly to wire/, and thus 
cut out all the series field coils and then the motor will run as a 
plain shunt-wound machine, and its speed will be the highest it 
can attain. 

If the reversing drum and switch M are now revolved to the 
position shown in the diagram, the circuit through the motor will 
be broken and the machine will come to a state of rest. If the 
reversing drum and M are now revolved in the opposite direction, 
that is, contrary to the movement of the hands of a clock, the 
brushes g and h will rest on one of the revolving dram segments, 
and i and k on the other segment. If the path of the current is 
now traced it will be found that it will enter the armature through 
wire E, and the left side, instead of through wire J, as in the pre- 
vious case. It will also be found, however, that the current after 
passing through the armature will reach the series field coils 
through F, which is the same path as before, so that the direction 
of the current has been reversed through the armature only, 
which is what is required to reverse the direction of rotation of 
the motor. Whichever way the switch M and the reversing drum 
are turned, the direction of the currents through the series field 
coils and the shunt field coil will be the same, and only the arma- 
ture current will be reversed. 

Cutting out the series field coils not only increases the speed 

47 



738 HANDBOOK ON ENGINEERING. 

of the motor, but obviates the danger of the ear attaining a dan- 
gerously high speed if the load is being lowered. A shunt wound 
motor will run as a motor up to a certain speed, but if the veloc- 
ity is forced above this point by driving the machine by the ap- 
plication of external power, then the motor will begin to act as a 
generator, and as it takes power to run a generator the motor will 
begin to hold back. Now if an elevator car is running down 
with a heavy load, the load will draw the car down, and unless a 
resistance of some kind is interposed, the speed will become 
greater and greater as the car descends, and by the time it 
reaches the bottom of the shaft it may be running at a velocity 
almost equal to that attained by a free fall. The power required 
to drive the motor when acting as a generator serves to hold the 
car back, for the current developed increases very rapidly with 
increase of speed, so that an increase of speed of ten or fifteen 
per cent above the normal running velocity will be about as much 
as can be reached even with an extra heavy load. 

Although the motor will act as a generator and hold the car so 
that it cannot attain a dangerous speed when descending under 
the influence of a heavy load, it will only accomplish this result 
when the circuit is closed ; for if the circuit is Open there will be 
no power generated ; hence, no power will be absorbed by the 
motor. As can be readily seen, it is possible for the circuit out- 
side of the motor to become broken by the melting of a fuse or 
some other cause, and if this occurs when the car is coming down 
with a heavy load there might be a serious accident. To obviate 
such mishaps the main switch is made with a magnet b which 
holds the switch closed so long as current passes through it, but 
allows the switch to swing open if the line current disappears. 
This switch on this account is called a potential switch, because 
it is arranged to be actuated by the difference of potential be- 
tween the two sides of the line. When the line current fails, and 
the potential switch opens, the blade m comes into contact with n 



HANDBOOK ON ENGINEERING. 739 

and thus the circuit for the motor armature is closed through the 
resistance wire s which is connected with contact 7. This con- 
nection short circuits the armature through a resistance sufficient 
to keep it from being burned out, but not enough to prevent the 
motor from acting as a brake and holding the car down to a safe 



The wire c c which runs from magnet b of the potental switch, 
it will be noticed, connects with a coil marked- safety brake mag- 
net. This magnet acts normally to hold the brake off when the 
machine is running, but>if the current passing through it dies out, 
then it acts to put the brake on. Now, as has already been ex- 
plained, when the current is flowing in the main line, there is a 
current passing through coil b of the potential switch ; hence, 
there is a current passing through the coil of the safety magnet for 
the brake ; but if the line current fails the current through the 
brake magnet will also fail and the brake will go on ; so that the 
car will be doubly protected, one protection being the short cir- 
cuiting of the motor circuit through wire s, and the other the ap- 
plying of the brake by reason of the failure of the current to flow 
through the safety brake magnet. 

As to directions for the proper care of these machines, very 
little need be said, as they are simple and substantial in con- 
struction and give very little trouble. The motor proper requires 
the same attention as is given to any stationary motor, that is, 
the commutator and all other parts must be kept as clean as pos- 
sible and the brushes must be properly set. As to the other 
parts, all that need be said is that the bearings must be well lubri- 
cated and free from grit. They must be tight enough to not al- 
low the parts to play, but at the same time care must be taken 
that they are not so tight as to heat up or cut. All bolts and 
nuts must be regularly examined and kept tight, so that they 
may not work loose or out of place. The most important point 
to observe, however, is not to undertake under any circumstances 



740 HANDBOOK ON ENGINEERING. 

to tinker with the sheave wheel and the gears that connect it with 
the horizontal bar that operates the brake and controller 
switches. Neither must the brake or the switches be disturbed. 
All that is to be done to the latter is to keep the contacts bright 
and clean. If any of these parts, from the sheave wheel to the 
controller switches, get out of set, so that the machine will not 
run satisfactorily, do not undertake to readjust them, but send 
for an expert from the elevator company. If any of these parts 
are removed or shifted there is danger of their not being put 
back in their proper position, and if they are misplaced a very 
serious accident may be the result. If the proper adjustment of 
these parts is destroyed, the elevator will not stop automatically 
at the top and bottom landings, but will run too far at one end 
and stop short of the mark at the other ; hence, the car may 
either strike violently against the floor or run at full speed into 
the overhead beams, and in either case the results might be very 
serious. Even elevator experts have to go cautiously in adjust- 
ing the position of the sheave wheel and the parts connected 
with it. 

The fact that those not thoroughly posted in the operation of 
these elevators should not tamper with the hand rope sheave and 
its connections, is not at all unfortunate, for it is next to impos- 
sible for them to get out of place ; bat special caution is advised 
at this point, because there are many men who are apt to take it 
for granted that if the machine runs poorly from some trifling 
cause that they have not been able to locate, the trouble must be 
due to some defect in the adjustment of the several parts of the 
operating sheave and its connections. They will then proceed to 
pull the machine apart, and when they put it together again they 
are very liable to get it connected wrong, and if such should be 
the case the first trip made by the elevator might end seriously. 

Although the machine described in the foregoing works in an 
entirely satisfactory manner, it has been superseded almost en- 



HANDBOOK ON ENGINEERING. 



741 



tirely in first-class installations of recent date by machines that 
are controlled by means of a small switch in the car instead of 
the hand rope. There are several types of such elevators made 
by the Otis Company, one of the latest designs being shown in 
Fig. 8. 




Fig. 8. 

As will be noticed at once, this machine is different in several 
respects from" the hand rope control machine shown in Fig. 6. As 
the machine is controlled by the movement of a switch in the car, 
the brake cannot very well be actuated mechanically, hence a 
magnetic brake is provided, the magnet being seen at the top of 
the stand to the right of the motor. The automatic stopping de- 
vices and the slack cable stop are also arranged so as to act upon 



742 



HANDBOOK ON ENGINEERING. 



switches, which are contained within the casings seen at the front 
end of the hoisting drum. The controller for this type of 
machine is not placed on top of the motor, generally, for since it 



CONTROLLE/f 




CT^y 



9. 



is not connected mechanically with any of the moving parts of the 
machine, it can be located at any convenient point, and is then 
connected with the motor armature, field coils and with the brake 



HANDBOOK ON ENGINEERING. 743 

magnet and automatic stop switches by means of copper wires. 
The controller used with this type of machine is arranged after 
the fashion of a switchboard, the switches being located on the 
frpnt, and the connecting wires, together with the starting resist- 
ance, being at the back. The switches are actuated by means of 
electromagnets, and on that account the device is called a magnet 
controller. The diagram of the wiring connections with this con- 
troller is more complicated than that for the hand rope controller, 
but for the purpose of simplifying the drawing as much as pos- 
sible I have removed all the connections that are not actually 
necessary for a proper understanding of the general arrangement 
of the circuits. This simplified diagram is shown in Fig. 9. 

The front of the controller is shown in Fig. 10, and the back 
of same in Fig. 11, the starting resistance being removed in this 
illustration so as to afford a clear view of the wire connections. 
The side of the starting resistance can be seen in Fig. 10. In 
this last named illustration, all the switches are in the position 
they take when the elevator is stopped. The two large switches 
on either side at the bottom of the board are the starting switches, 
one acting to run the car up and the other one to run it down. 
The two smaller switches occupying the center of the bottom 
panel of the board and the two switches in the upper corner are 
for the purpose of accelerating the velocity of the motor when it 
is started. When the motor starts, there is a resistance in the 
armature circuit, and the current after passing through the arma- 
ture is passed through series field coils. After the motor has 
started, the starting resistance is cut out, and then the series field 
coils are cut out, so that when the full speed is attained, the 
motor is a simple shunt- wound machine. In this respect the 
arrangement of the motor circuits is the same as in the hand rope 
controller machine. 

When it is desired to start the car, a small switch in the latter 
is moved toward the right or left, according to the direction in 



744 



HANDBOOK ON ENGINEERING. 



which the car is to move. To run the car up, the car switch is 
turned to the left, and this movement sends a current through the 
magnet of the lower right side magnet on the controller board. 




Fig. 10. 

This magnet then lifts its plunger and the two discs mounted upon 
the latter come into contact with the stationary connectors located 
just above them, and then the current can find its way through 



HANDBOOK ON ENGINEERING, 



745 



the motor circuits in the proper direction to produce the upward 
motion. The four small switch magnets on the controller board 
are connected in separate circuits that are in parallel with each 



~T 




Fig. 11, 

other, and in shunt relation to the armature of the motor. When 
the motor first starts, the counter electromotive force developed 
by the armature is not as great as when it is running at full speed, 



746 HANDBOOK ON ENGINEERING. 

because a portion of the electromotive force of the line current is 
used to force the current through the starting resistance and 
through the series field coils. When a portion of the starting 
resistance is cut out the armature counter electromotive force is 
correspondingly increased. When more of the starting resistance 
is cut out, the counter electromotive force is further increased. 

It is still further increased when the series field coils are cut 
out. Now the current that passes through the magnets of the 
four small switches on the controller board increases as the counter 
electromotive force of the motor armature increases. The mag- 
nets are so adjusted that as the currents passing through them 
increase one after the other will lift its plunger and then the con- 
nections made by the discs at the lower end of these plungers will 
cut out successively the sections of the starting resistance and the 
sections of the series field coils. The two small tubes at the top 
of the controller board are safety fuses, and the line wires are 
connected with their upper ends. 

By the aid of the foregoing explanation of the way in which 
the controller acts, the following description of the wiring diagram 
(Fig. 9) will be easily understood. In this diagram the line 
wires come in at the top of the controller and are marked + an d 

. The motor is shown at the bottom of the diagram, the circle 

A representing the armature, and the coil B is the brake magnet. 
The stop motion switch is placed on the elevator machine, in one 
of the casings at the front end of the drum, and is actuated by 
the automatic stop mechanism which stops the car at the top and 
bottom landings. The car switch is shown in the upper left hand 
corner of the diagram, and the curved lines </ represent the wires 
that connect it with the motor and the controller board. These 
wires are placed within a flexible cable that is attached to the 
side of the elevator shaft half the way up from the bottom, the 
cable being long enough to reach the car when at either end of 
the shaft. The limit switch in the car is for the purpose of stop- 



HANDBOOK ON ENGINEERING. 747 

ping the motor, if the car reaches either end of its travel without 
being stopped by the operator, or the action of the stop motion 
switch. This switch is closed under ordinary conditions, so that 
the current in wire C can flow all the way to the lower contact a 
of the car switch. If it is desired to run the car down, the car 
switch is turned to the right, and then wire C is connected with 
wires D ' and FD. The stop motion switch is normally in the 
position shown so that the current in wire D ' can pass to D and 
following this wire it will reach contact D which is under the 
lower disc of the right side starting switch. Through the disc 
this contact is connected with the corresponding contact on the 
other side of the disc, and this latter contact is connected with a 
wire that carries the current to the magnet of the left side starting 
switch. Considering now the main current in the -j- line it can 
be seen that it can flow down to the line near the bottom of the 
controller portion of the diagram, and which terminated in the 
-j- contacts of both the starting switches, but can go no further 
so long as the discs on the plungers of the magnets are in the 
lower position. As soon, however, as the current coming from 
the car switch passes through the magnet of the left side switch, 
as just explained, the plunger will be lifted, and then the disc will 
connect the + contact with the S2 contact, and also with a 
smaller contact B. When this connection is made, the main cur- 
rent can flow from contact S2 to contact S2 of the right side 
switch , and thence through the connecting disc to contact I which 
is connected by wire to binding post I; the latter being con- 
nected with the right side armature terminal I. After passing 
through the armature the main current reaches binding post E 
and through the connecting wire the contact E at the top of the 
left side starting switch, and as the plunger of this switch is in 
the raised position, the current can pass to contact R and thus 
reach the upper end R of the starting resistance in the resistance 
box. 



748 HANDBOOK ON ENGINEERING. 

From the end F of the starting resistance, the main current 
flows to binding post F and then to the F end of the series field 
coils, and from end H to binding post II and to the — line wire 
at the top of the diagram. The current for the shunt field is 
taken from the contact S2 at the bottom of the left-ride starting 
switch, and passes to point #4 and thence to D and to the D end • 
of the shunt field coil, and through this coil to end H of the series 
coil, and thus to the — line. The current for the brake magnet 
starts from the small contact B at the bottom of the left-side 
starting switch. 

The car switch when moved will first cover contact D' so that 
the main current will follow the path outlined above, but as 
soon as the car switch covers contact FD, the current passing- 
through wire FD in the cable will reach the stop-motion switch 
and pass to F, and thus to magnet No. 1 at the upper left hand 
corner of the controller board. The lifting of this switch will 
cause Its disc to connect the contacts RR' and thus the current 
will pass to point R' of the resistance and cut out the upper sec- 
tion. The current from contact B at the bottom of the left-side 
starting switch passes through the magnet coils of the three 
switches, Nos. 2, 3 and 4. Now soon after the first section of 
the starting resistance is cut out, No. 2 magnet becomes strong 
enough to lift its plunger, and then the current from the right 
side, contact R, at the top of the left-side switch, will pass to 
contact E of No. 2 switch, and thus to R2 and to point R2 of 
the resistance, thereby cutting out two sections. In this way the 
current through magnet of switch No. 3 will be increased and the 
plunger will be lifted so that the current will be able to pass from 
the R contact of this switch to the G contact, and thus to binding 
post G and to the center of the series field coils, thereby cutting 
out one-half of these coils. In this way the current through coil 
of No. 4 magnet will be farther increased, so that it will be able 
to lift its plunger, and thus form a direct connection from contact 
G of switch No. 3 and the main wire leading to the — line. 



HANDBOOK ON ENGINEERING. 749 

Thus it will be seen that the four switches, 1,2, 3 and 4, will 
act one after the other. This same operation is repeated if the 
car switch is moved to the right, so as to run the elevator down, 
the only difference being that the starting switch at the right side 
of the board will be lifted, but the action of the four smaller 
switches will be the same. 

In addition to the operating circuits described in the foregoing 
there are wires that connect the slack cable switch with the motor 
circuits and other connections by means of which the elevator may 
be run from the controller board whenever desired. These con- 
nections are not shown in Fig. 9, as they would complicate the 
drawing, and it is not thought advisable to complicate the explan- 
ation of the main part of the system for the sake of introducing 
the minor details. 

This type of electric control is used for elevator building in- 
stalled in office buildings, and others placed where the car is oper- 
ated by a regular attendant. For private house elevators and for 
dumb waiters it is necessary to modify the controlling system so 
that the car may be operated not only from within, but also from 
any of the floors of the building. It is further necessary that 
the circuit connections be such that if the car is operated from 
any floor, it will run to that floor, whether above or below.it, and 
further, so that if it is being operated by a person within the car 
it cannot be operated by any one else from any of the landings. 
It must also be arranged so that if the car is set in motion from 
any floor it cannot be stopped or interfered with in any way by 
a person at another floor. For the purpose of safety the system 
must also be arranged so that the car cannot move away from any 
floor until the landing door is closed. This feature is necessary 
to guard against people falling through the open doorway into the 
elevator shaft. Although it would appear difficult to accomplish 
all these results without resorting to great complications, as a 
matter of fact the system used by the Otis Company is decidedly 



750 



HANDBOOK ON ENGINEERING. 




OOOR CONTACTS 



HANDBOOK ON ENGINEERING. 751 

simple. At each floor of the building a push button is placed, 
and by pressing this for an instant the car is set in motion wher- 
ever it may be, providing it is not being used by some other per- 
son, and when it reaches the floor from which it has been operated 
it will stop automatically. If the elevator is operated from the 
car, a button is pushed that corresponds to the floor at which it 
is desired to stop, the car will then begin to move, and when the 
floor is reached it will stop. If the jjassenger after stepping out 
of the car forgets to close the landing door, the elevator cannot 
be moved away from the landing by the manipulation of any of 
the push buttons on the various floors or within the car. The 
way in which all these results are accomplished can be made 
clear by the aid of Fige 12, which is a simplified diagram of the 
wiring. 

In this diagram most of the parts are marked with their full 
name. The floor controller is a drum which is revolved by the 
elevator machine and its office is to shift the connections of the 
wires 11, 22, 33, 44, from one side of the circuit DU to the 
other as the car ascends and descends in the elevator shaft. This 
shifting of these connections is necessary to cause the car to run 
down if above the landing from which it is operated, and to run 
up if it is below the landing. The actual position of the floor con- 
troller with reference to the elevator machine can be seen in Fig. 
13 in which the floor controller is located back of the motor and is 
driven from the drum shaft by means of a chain and sprocket wheel. 
In the diagram Fig. 12 it will be noticed that the drum surface is 
divided into two segments and upon one rests the brush of wire 
D while upon the other rests the brush of wire U. The twelve 
contacts shown at G form the operating switch. The center row 
marked m n o p are movable, and the four contacts above them 
as well as the four below are stationary. The center row of con- 
tacts m nop are moved upward by a magnet represented by the 
coil D and they are moved downward by another magnet repre- 



752 HANDBOOK ON ENGINEERING. 

sented by the coil U. From this it will be seen that if a current 
comes from the floor controller through wire D the movable con- 
tacts of G will be lifted and will connect with the top row, while 
if the current comes from the floor controller through wire II, the 
movable contacts will be depressed and will make connections with 
the lower row of contacts. 

The main switch that connects the motor circuits with the 
main line is shown at S. As will be noticed, a wire marked d -f- H 
runs from the -f- wire to the right side of the diagram, where the 
landing and the car push buttons and their connections are shown. 
This wire runs from top to bottom of the elevator shaft and is con- 
nected with switches that are closed when the landing doors are 
closed, and open when the doors are open. These switches are 
indicated by the four circles marked door contacts, the diagram 
being for a building four stories high. If the door contacts are 
closed, the current can pass as far as the wire marked -f- which 
runs through the flexible cable to the car. In the car there is a 
switch in this wire and further on a gate contact, which is closed 
when the car door is closed. If these switches are closed, the 
current can return from the car through wire A and run as far as 
the center of the diagram under the main switch S. The floor 
controller is shown in the position corresponding to the car at the 
bottom of the shaft. Suppose now that the landing push button 
I is pressed for a second, then the wires B and I will be connected, 
and the current in wire A will pass to wire B and through the 
push button to wire I and thence to wire 11. The coil between 
wire I and wire 11 is a magnet, and as soon as the current passes 
through it, it draws the contact to the right and thus provides a 
path for the current direct from wire A to wire 11, so that the push 
button may be raised without opening the circuit. The current 
in wire 11 will pass through the floor controller to wire £7 and thus 
through magnet U of the operating switch G. This magnet will 
then draw down the movable contacts m n o j), and the main line 



HANDBOOK ON ENGINEERING. 



753 



current from the + wire will pass from contact m to wire m' and 
through wire m' to point w, hence through wire w' to the acceler- 
ating, or starting resistance, and to wire F which leads to th3 
series field coils. Returning from these coils through wire H to 
magnet switch 2 and thence wire n' to contact n, and as this con- 




Fig. 14. 

tact is pressing against the one directly below it, the current will 
flow through the connection to wire E and thus to the armature ; 
returning from the latter through wire I and wire o' to the contact 
below o and thus to o and through the permanent connection to 
contact p and to the lower right hand contact which is connected 



754 HANDBOOK ON ENGINEERING. 

with wire r which runs to the — side of the main switch. The 
shunt field current is derived from wire m' and returns to contact 
p and thus to wire r through wire p' , as can be clearly traced. 
The brake magnet current starts from the left side contact of G 
through wire -f- B and returns directly to the lower end of 
wire r. 

The magnet switches 1 and 2 act in the same manner as those 
in diagram Fig. 9, that is, by the increase in the counter electro- 
motive force of the armature which causes the current that passes 
through them to increase in strength. When magnet I closes its 
switch, the current passes from wire w' to wire F and thus the 
accelerating resistance is cut out. When magnet 2 closes its 
switch the current passes from wire m" directly to n! and thus to 
the armature without going through the series field coils ; thus 
the latter are cut out. 

Returning now to the operation of the floor controller it will be 
seen that as the current is flowing through wire 11 the circuit will 
be broken if the controller is rotated until the gap at the top 
comes under the brush of wire 11. Now the floor controller 
drum begins to turn as soon as the elevator machine moves, and 
it is so geared to the elevator drum that when the car comes op- 
posite the first floor the brush of wire 11 will be over the upper 
gap, and then the circuit will be open and the magnet U will be 
de-energized and allow switch G to move back, to the stop position. 

If button No. 4 is pressed instead of No. 1 the car will not 
stop until the gap at the top of the floor controller drum comes 
under the brush wire 44, for the circuit between this wire and 
wire U will be closed until that position is reached. 

If the car is run up to the fourth floor, as the gaj:> at the top 
of the floor controller drum will then be under the brush of wire 
44, the brushes of wire 11, 22 and 33 will rest upon the same 
segment as the brush of wire D; therefore, if with the car at 
the top floor a button is pressed at any one of the lower floors 



HANDBOOK ON ENGINEERING. 755 

the current will pass from its corresponding wire to wire D and 
thus through magnet coil D and to wire r' and wire r. The cur- 
rent passing through magnet D will draw the movable contacts of 
the operating switch 6 upward, and thus set the elevator machine 
in motion in the opposite direction from that "in which it runs 
when the U magnet is energized. 

In tracing out the circuits from the floor push buttons as just 
explained it will be noticed that if any one of them is depressed, 
the current in wire A will flow through wire B to the button de- 
pressed, and then enter the wire returning from that button. 
When the car buttons are depressed the current in wire A will 
pass to wire C and then through the button in the car to the 
proper return wire ; that is, to one or the other of the wires 
1, 2, 3, 4. After entering one of these four wires the current 
follows the same path as it does when one of the floor buttons 
is depressed. The magnet B' in the B wire, and the 
magnet C in the (7 wire, are for the purpose of preventing in- 
terference between a person operating the elevator from within 
the car and another one at one of the landings. The B' switch is 
actuated by a magnet that is wound with two coils that act in 
opposition to each other. These coils are shown to the left of B '. 
When the elevator is operated from one of the floor push buttons 
the current in wire A passes through both the coils on the magnet 
of switch B' and as one coil counteracts the other the switch 
is left closed and the current passes directly to wire B. If the 
elevator is operated from within the car the current from wire A 
in passing to wire C passes through one of the coils of the mag- 
net that actuates switch B', hence this switch is opened and the 
connection with wire B is broken, so that if now any one of the 
floor buttons is pressed it will have no effect as the circuit is 
opened at switch B' . The current flowing through wire C passes 
through a magnet that acts to close the switch C and thus allow 
a portion of the current to pass directly to wire r. This current 



756 HANDBOOK ON ENGINEERING. 

will continue to flow even after the car has stopped at the landing, 
providing the door is not opened. As soon as the door in the 
car, or the landing door, is opened the circuit is broken either in 
wire Hov in wire A, and then the car cannot be moved until the 
doors are closed. If it were not for switch C it would be possi- 
ble for a person at one end of the landings to move the car if he 
pressed the button during the short interval of time between the 
stopping of the car and the opening of the landing door. The 
opening of the door would stop the car, but by this time it might 
be a foot or two away from the floor level. The current that 
passes from switch C" to wire r is kept down to a small amount 
by passing it through a high resistance which in the diagram is 
marked 700 w. 

The electrical portion of the Otis electric elevators has been 
supplied for many years to four or five of the leading companies, 
which were controlled by the Otis, and during the last two or 
three years it has been supplied to practically all the prom- 
inent makers, as these are now part and parcel of this 
company ; hence the descriptions given in the foregoing 
are more than likely to cover any case met with in 
practice, for although there are numerous small manufacturers, 
the sum total of their elevators in use is comparatively small. 
The only electric elevators in addition to those described in the 
foregoing that have come into extensive use are those made by the 
Sprague Electric Co. 

These maehines are of two different types, one being the ordi- 
nary drum design, and the other the screw machine. The drum 
machine is similar in its main features to the same type of ma- 
chine of other makers, and it is only in the minor details of con- 
struction that any radical difference can be noted. In the means 
employed for controlling the motion of the motor, however, there 
is a decided difference. In all the Sprague elevators the car is 
controlled electrically, hand rope control not being used in any 



HANDBOOK ON ENGINEERING. 



757 







758 HANDBOOK ON ENGINEERING. 

case. The drum machines are arranged like those of other makes, 
so that the motor is connected with the main line whether the car 
is going up or down, and acts as a motor or as a generator ac- 
cording to the conditions of the load ; that is if the load is lifted, 
the machine acts as a motor, and if the load is lowered, the ma- 
chine acts as a generator and holds the car back. With the screw 
type of machine, the arrangement is different, the motor acting 
as such in raising the load, but on the descent the motor is dis- 
connected with the main line and acts as a generator, developing 
a current that circulates in a circuit formed by the motor connect- 
ing the wires, and which is entirely independent of the main 
line. In the drum machine, when the motor acts as a generator 
in lowering a load, the current it generates is sent back into the 
main circuit, and at all times the machine is connected with the 
main line, while with the screw type the motor is only connected 
with the mainline when the load is lifted. 

The general appearance of the screw type of Sprague elevator 
is shown in Fig. 14. This illustration represents two machines, 
one placed on top of the other. In buildings where there is an 
abundance of floor space, the machines are all set directly upon 
the floor, but where floor space is limited, they are stacked two, 
three and even four high. 

As can be clearly seen in Fig. 14, a long screw is coupled to 
the end of the motor armature shaft. This screw threads through 
a nut that is mounted in a cross head that carries a number of 
sheaves around which the lifting ropes pass. At the extreme end 
of the machine other sheaves are mounted, these being held in 
stationary supports. The sheaves carried by the cross head 
travel from one end of the machine to the other as the screw is 
rotated. When they are drawn away from the stationary sheaves 
the elevator car is raised, and when they move toward the sta- 
tionary sheaves the elevator is lowered. In this respect the 
action is just the same as in a horizontal cylinder hydraulic ele- 
vator. 



HANDBOOK ON ENGINEERING. 



759 




Fig. 15. 



760 HAND BOOK ON ENGINEERING. 

The nut carried by the traveling cross head is so arranged that 
when the latter reaches the end of its travels at either end of the 
screw, the nut is released and then rotates with the screw with- 
out moving the cross head. This forms a perfect top and bottom 
limit stop, for even if the motor continues to run, the car cannot 
be carried beyond the positions corresponding to the points at 
which the nut slips around in the cross head. 

The brake for holding the machine is mounted upon the outer 
end of the armature shaft, and can be seen at Fig. 14 at the ex- 
treme right hand side. This brake is actuated by a magnet that 
releases it, and a spring that throws it on. When the current is 
on, the brake is lifted and when the current is off the brake goes 
on. In this respect, the action is the same as in all other electric 
elevators. 

The operation of the motor is controlled by a small switch in 
the car, which is connected with the motor circuits by means of 
wires contained in a flexible cable, just like the Otis electrically 
controlled machines. The controller consists of a main switch i 
which is moved by a small motor called a pilot motor, and a num- 
ber of smaller magnetic switches whose action will be presently 
explained. All these parts are mounted upon a switchboard, and 
present the appearance shown in Fig. 15. The pilot motor and 
main switch are located at the top of the board, and the magnet 
switches cover the space below, while the starting and regulating 
resistance is mounted on the back of the board. 

The complete wiring diagrams for these machines is decidedly 
complicated owing to the fact that there are numerous switches 
and devices whose office is to afford additional safety, or to ren- 
der the control more perfect. When all the parts that are not 
actually necessary to illustrate the system are removed, however, 
the diagram becomes quite simple and can be readily understood. 
JSuch a diagram is shown in Fig. 16. This diagram shows the 
motor together with the screw and sheaves, the elevator car, the 



HANDBOOK ON ENGINEERING. 761 

counterbalance, and the operating switches. The wires marked + 
and — are connected with the main line. The switch in the car 
is connected with the controller by means of four wires, marked 
cb d and s. The lower one of these wires, marked s, is connected 
with the stud around which the car switch swings. When the 
car switch is moved onto the upper contact, it connects wire s 
with wire c and then the car runs up. When the car switch is 
moved down onto the lower contact, wire s is connected with wire 
d, and then the car runs down. When the car switch is placed in 
the central position wire s is connected with wire b and then the 
elevator stops. The two switches marked " up limit," "down 
limit," are for stopping the car automatically at the top and bot- 
tom landings. Normally the up limit switch is closed and the 
down limit switch is open. With these switches in this position, 
which is the position in which they are shown in the diagram, the 
current from the -f- wire can pass through the up limit switch to 
wire &, and thence through wire I to the armature of the motor, 
and then through the field coils, and reach wire m. It cannot go 
beyond this point until the switch C is moved. This is the main 
operating switch, which in Fig. 15 is seen at the top of the board, 
the contacts being arranged in two circles. The pilot motor that 
rotates the arm of this switch, which is clearly shown in Fig. 15, is 
represented in this diagram, Fig. 16, at A. As will be seen in 
this diagram, this motor has a field provided with two magnetizing 
coils, one for the up motion, and one for the down motion, and in 
addition it is provided with a brake to stop it quickly and hold it 
when not in use. The portion of the diagram marked B is the 
reversing switch. 

Let us suppose now that the car switch is moved upward, so as 
to cause the elevator, to ascend, then wire s will be connected with 
wire c. From the + wire a current will pass through wire a to s 
and thus to c, and through magnet e of switch g, thus closing this 
switch so as to connect wires h and i. The current in wire c will 



762 



HANDBOOK ON ENGINEERING. 



pass to B and through the connecting plate u will reach the end 
of the up field coil of the pilot motor, and then pass through the 
armature of this motor, and finally through the magnet that re- 
leases the brake. The pilot motor will now rotate the reversing 
switch B so that the contact plates will move toward the left. 
This movement will bring plate w under the ends of wires s and t, 
thus permitting a current from s to pass to i, and as switch g is 



J3RAKE RELEASE 




$ PRAGUE PRATT SCREW ELEVATOR 



closed this current will reach wire h and thus the magnet j, 
thereby lifting the plunger switch that closes the gap between 
wire q and the — wire. As the arm of the main switch C 
moves with the reversing switch J3, this arm will ride over the 
contacts on the right side, marked " U res." and thus the current 
from wire m will be able to reach wire q after passing through the 
up resistance. 



HANDBOOK ON ENGINEERING. 763 

If the car switch is left on the upper contact, the pilot motor 
will continue to rotate until the arm of switch G reaches the top 
of the resistance contacts, marked Full up. When this point is 
reached, the contact plate u of the reversing switch B will pass 
from under wire c and the terminal of the up field of the pilot 
motor, and then this motor will stop rotating. 

If the car switch is not kept on the upper contact very long, 
the pilot motor can be stopped with the arm of switch G at some 
intermediate point on the resistance contacts, thus by the time 
during which the car switch is kept upon the upper contact, the 
amount of resistance cut out of the motor circuit can be con- 
trolled and thereby the speed of the car can be controlled. 

In this operation it will be noticed that the motor is connected 
with the main line and that the current enters through the -f- wire 
and passes out through the — wire. If now we turn the car 
switch downward, the s wire will be connected with the d wire and 
by following the latter to the reversing switch B it will be seen 
that through connecting plate v it is connected with wire z which 
leads to the end of the down field of the pilot motor, thus setting 
the latter in motion in the opposite direction so as to shift the 
contact plates of B toward the right, and at the same time rotate 
the arm of the main switch C to the left, thereby making contact 
with the contacts of the down resistance. With the arm of G in 
this position , it will be seen that the current in wire I can flow 
through the motor armature and field and through wire m to the 
arm of switch G and through the. down resistance to wire n and 
thus back to wire I, thereby forming a closed circuit within the 
motor wires and connections, and disconnected from the main line 
except on the side of the + wire. The rotation of B causes the 
connecting plate x to ride upon the terminals of wires s and t, and 
thus a current is sent through the brake magnet so as to lift the 
brake, and allow the elevator machine to run. When the pilot 
motor moves the arm of G so far as to reach the top of the down 



764 HANDBOOK ON ENGINEERING. 

resistance, the contact plate v of the reversing switch B will pass 
beyond the terminals of wires d and z, thus breaking the circuit 
of the pilot motor and bringing the latter to a stop. 

"When the reversing switch B is in the stop position, as shown 
in the diagram, the terminal of wire b does not rest upon a con- 
necting plate but when the switch is rotated for the up motion, the 
terminal of b rests on plate v so that if the car switch is turned 
to the stop position, the current from wire b will pass to wire 
z and thus reverse the direction of rotation of the pilot 
motor, and return the switches to the stop position. If 
the car is running down, when the car switch is turned 
to the stop position, the current from wire b will pass to 
wire z and thus reverse the direction of rotation of the pilot 
motor, and return the switches to the stop position. If the car 
is running down, when the car switch is turned to the stop posi- 
tion, the wire b will ride over the plate u and thus the current 
will pass through the pilot motor through the up field and thus 
rotate the switches back to the stop position. In each case, as 
will be noticed, whenever the current flows through wire b it ener- 
gizes coil / and thus opens switch g. When the car is running 
up the current for the brake magnet passes from wire i through 
the switch which is energized by the main current flowing in wire q. 
When the car runs too far down, and closes the down limit switch, 
the motor circuit becomes closed through wires p, r and k, thus 
giving another path for the current generated by the motor arma- 
ture and thereby increasing the resistance to rotation. 

The controller for the Sprague drum machines is very similar 
to the one just described. It is operated by a pilot motor, and 
in so far as the controller switchboard is concerned looks the 
same. The only difference is that rendered necessary by the 
fact that in lowering as well as in raising the load, the motor is 
connected with the line. This requires a slight change in some 
of the wire connections. 



HANDBOOK ON ENGINEERING. 765 

The electrical parts of the Sprague elevators require very little 
attention other than to keep them clean and all the contacts bright 
and in proper adjustment, so that when moved a good contact 
may be made. Of the mechanical portion, the drum machines 
require about the same attention as other machines of this type. 
As to the screw machines, the part that requires most attention is 
the screw and the nut. As can be readily understood, if the nut 
were solid, the friction against the screw would be very great ; 
therefore, to reduce this friction, the nut is made so as to carry a 
large number of friction balls. These run in a groove cut in the 
side of a thread and roll between the thread and the screw and 
the thread in the nut. A tube is attached to the nut to provide a 
path through which the friction balls can pass from the end of the 
thread to the beginning, thus making an endless path in which 
they move. As these friction balls are subjected to a heavy pres- 
sure, there is more or less danger of their giving trouble and on 
that account the thread on the screw should be carefully examined 
and kept as clean and free from grit as possible. Under favorable 
conditions these screws run very well, the wear being trifling, but 
in some instances they are liable to cut badly, hence they should 
be closely watched. 



DIRECTIONS FOR THE CARE AND OPERATION OF THE 
ELECTRIC ELEVATORS. 

Whenever the attendant wishes to handle the machine to clean, 
adjust, repair or oil it, he should see that the current is shut off 
at the switch, and thus prevent all possibility of accident. 

Cleaning". — Keep the entire machine clean. Clean the com- 
mutator and other contacts and brushes carefully with a clean 
cloth and keep them free from grease and dirt. If the face of the 
rheostat on which the rheostat arm brushes work becomes burnt, 
clean with a piece of fine sand-paper (No. 0), or if necessary use 



766 HANDBOOK ON ENGINEERING. 

a fine file. Keep all contacts smooth. Try the rheostat arm 
when cleaning to be sure that it moves freely off contacts. 

Oiling* — Oil the drum shaft bearings with good heavy oil. 
Oil the worm and gear by filling the chamber around them with a 
mixture of two parts of good castor oil and one part good cylinder 
oil. Keep this chamber filled to the top of worm or mark on 
gauge glass, adding a little each day as it is used. The end 
thrust bearings of the machine are automatically oiled from this 
chamber. This should be drawn off every two or three months 
and replaced by fresh oil. Oil the motor bearings with dynamo 
oil. These are automatically oiled, but should occasionally be 
supplied with fresh oil. Lubricate the commutator, rheostat face, 
drum switch and contacts veky sparingly with a cloth moistened 
with oil. Care should be taken not to supply too much oil to 
these parts. Keep the oil dash-pot, if any, sufficiently filled with 
oil to allow the rheostat arm to move quickly on to the first con- 
tact and to retard this movement beyond this contact. The best 
oil for this purpose is fish oil, or some thin oil that is not readily 
affected by changes in temperature. If an air dash-pot is used, 
keep it slightly oiled so as to keep the packing soft. Keep all 
parts of the elevator, including sheaves, guides, cables, etc., clean 
and well oiled. 

Operating* — Before switching the current on to the machine, be 
sure that the operating lever is in its central position. To ascend, 
draw the lever the full throw to the up . To descend , draw the lever 
the full throw to the doivn. To run at slow speed, bring the lever 
toward the center according to the speed desired. To stop, bring 
lever to slow speed when within four feet of landing, and to its 
central position when close to it. In this way, the operator can 
make accurate stops. When starting (machines on which the 
solenoid is used) if the current is admitted to the motor too 
rapidly, thereby starting the car with a jerk, or momentarily dim- 
ming the lights on the circuit, check the speed with which the 



HANDBOOK ON ENGINEERING. 767 

resistance is cut out of the armature circuit by slightly easing off 
the weight which acts in opposition to the core of the small 
solenoid. This solenoid controls a valve in the dash-pot and 
thereby regulates its speed in proportion to the current passing. 
If a governor starter is used and the current is admitted too 
rapidly, tighten the governor spring on the armature shaft, or 
close the vent in air dash-pot. If the car refuses to ascend 
with a heavy load, immediately throw the lever to the center 
and reduce the load, as in all probability it is greater than 
the capacity of the elevator. If it refuses to ascend with 
a light load, throw the lever to the center and have the 
fusible strip examined. If, in descending, the car should 
stop, throw the lever to the center and examine safeties, 
fusible strip and machine, and before starting, be sure that the 
cables have not jumped from their right grooves. If the car 
refuses to move in either direction, throw the lever on the center 
and have the fusible strips examined. Never leave the car with- 
out throwing the lever to the center. If the car should be stalled 
between floors, it can be either raised or lowered by raising the 
brake and running it by turning the brake-wheel by hand. Such 
a stoppage might be caused by the current being shut off at the 
station, undue friction in the machine, too heavy a load, fuses 
burnt out, or a bad contact of the switches, binding posts or elec- 
trical connections. If the car by any derangement of cables or 
switch cannot be stopped, let it make its full trip, as the auto- 
matic stop will take care of it at either end of the travel. The 
bearings should be examined occasionally to insure no heating 
and proper lubrication. 

General directions* ; — Have the machine examined occasionally 
by someone well posted in electric motors and elevators. The 
attendant should inspect the machine often. All brushes and 
switches should be sufficiently tight to give a good contact, but 
no tighter. None of the brushes should spark when in their 



768 HANDBOOK ON ENGINEERING. 

normal position. When the brushes become burnt dress with 
sandpaper or file, or, if necessary, replace with new ones. If 
brushes spark, dress with . sandpaper or file to a good bearing, 
and, if necessary, set up springs, but do not make the ten- 
sion such as to interfere with their ready movement. Adjust 
commutator brushes gradually for least sparking. These should 
be close to the central position. Contacts and brushes should 
be kept clean and smooth and lubricated sparingly. While 
replacing a fusible strip, be sure that main switch is open, and be 
careful not to touch the other wire with your tool or otherwise, as 
such contact would be dangerous. Never put in a larger fuse 
than the one burnt. Inspect the worm and worm-wheel occasion- 
ally through hand-holes in casing, to see that they are well lubri- . 
cated, and that no grit gets into the oil. They should show no 
wear. The stuffing box on the worm shaft should be only tight 
enough to keep the oil from leaking out of the worm chamber. 
Be sure that all parts are properly lubricated, and that none of 
the bearings heat. To make sure that the car and machinery run 
freely, lift brake lever and then rotate worm shaft by pulling on 
the brake wheel. The empty car should ascend without any exer- 
tion. Keep operating cables properly adjusted. Open main 
switch when the elevator is not in service. 



HANDBOOK ON ENGINEERING. 



769 



CHAPTER XXVI. 



HYDRAULIC ELEVATORS. 



The purpose of these pages is to furnish such instructions and 
information as will be of use to engineers in the handling of eleva- 
tor machinery. To accomplish this end, cuts and sectional views 
of cylinders and valves of the different types of elevator machin- 
ery made by the different elevator companies, are herein produced, 




so as to make the different elevators plain to the engineer. It 
must be borne in mind that the one point of paramount impor- 
tance for the successful operation of an elevator is proper care 
and management ; a lack of thorough knowledge of the machine 
and lack of attention in this respect shortens the life of the ma- 
chine and often makes extensive repairs necessary. 



HOW TO PACK HYDRAULIC VERTICAL CYLINDER 
ELEVATORS. 

Packing vertical cylinder piston from top* — Run the car 
to the bottom and close the gate valve in the supply pipe. Open 
the air cock at the head of the cylinder, and also keep open the 



770 



HANDBOOK ON ENGINEERING. 

2^1 




Showing how to set the rope on the lever elevator ; the sheaves 
want to be on the center of the travel, as shown. 



HANDBOOK ON ENGINEERING. 771 

valve in the drain pipe from the side of the cylinder long enough to 
drain the water in the cylinder down to the level of the top of the 
piston. Now remove the top head of the cylinder, slipping it and 
the piston rods up out of the way, and fasten there. If the piston 
is not near enough to the top of the cylinder to be accessible, attach 
a rope or small tackle to the main cables (not the counter-balance 
cables) a few feet above the car, and draw them down sufficiently 
to bring the piston within reach. Remove the bolts in the piston 
follower by means of the socket wrench furnished for that pur- 
pose. Mark the exact position of the piston follower before re- 
moving it, so that there will be no difficulty in replacing it. On 
removing the piston follower you will find a leather cup turned 
upwards, with coils of |-inch square duck packing on the outside. 
This you will remove and clean out the dirt ; also clean out the 
holes in the piston through which the water acts upon the cup. 
If the leather cup is in good condition, replace it, and on the 
outside place three new coils of |-inch square duck packing, being < 
careful that they break joints, and also that the thickness of the 
three coils up and down does not fill the space by \ inch, as in 
such case the water might swell the packing sufficiently to cramp 
it in this space, thus destroying its power to expand. If too 
tight, strip off a few thicknesses of canvas. Replace the piston 
follower and let the piston down to its right position. Replace 
the cylinder head and gradually open the gate valve in the supply 
pipe, first being sure that the operating valve is on the down 
stroke or it is so the car is coming down. As soon as the air has 
escaped before closing the air cock to make sure the air is all out 
of the cylinder, make a few trips, and the elevator is ready to 
run. 

Packing the vertical cylinder valves* — To pack the valve, 
run the car to the bottom and close the gate valve in the supply 
pipe. Then throw the operating valve for the car to go up, open 
the air cock at the head of the cylinder and the valve in the drain 
pipe at the bottom, and the water will drain out of the cylinder. 



772 



HANDBOOK ON ENGINEERING. 




Section of Elevator Cylinder and 
Valve Showing Working Parts. 

^ c 




OTIS VERTICAL HYDRAULIC PASSENGER AND FREIGHT MACHINE. 

A shows the position of the valve at rest. B shows the position of the valve when the car is going 
up or hoisting. C shows the position of the valve when the car is coming down or lowering. 



HANDBOOK ON ENGINEEKING. 773 

When the cylinder is empty, reverse the valve for the car to run 
down, so as to let the water out of the circulating pipe. In cases 
of tank pressure, where the level of the water in the lower tank is 
above the bottom of the cylinder, the gate valve in the discharge 
pipe will have to be closed as soon as the water in the cylinder is 
on a level with that in the tank, allowing the rest to pass through 
the drain pipe to the sewer. As soon as the water has all drained 
off, take off the valve cap and remove the pinion shaft and sheave, 
marking the position of the sheave and the relation which the 
teeth on the pinion bear to the teeth on the rack before removing. 
You can now take out the valve plunger and put the new cup 
leather packings on in the same position as you find the old ones. 
Replace all the parts as first found. Before refilling the cylinder, 
close the valves in the drain pipes, but leave the air cock at the 
head of the cylinder open and be careful that the operating valve 
is in position* for the car to go down. Gradually open the gate 
valve in the supply pipe. When the cylinder has filled with water 
and the air has escaped, close the air cock and open the gate 
valve in the discharge pipe. 

Packing piston tods. - Close the gate valve in the supply pipe. 
Remove the followers and glands to the stuffing boxes and clean 
out the old packing. Repack with about eight turns of J inch flax 
packing to each rod, and replace glands and followers. Screw 
down the followers only tight enough to prevent leaking. 

Packing Otis Vertical Piston from bottom. - Remove the 
top stop-button on hand rope and run the car up until the piston 
strikes the bottom head in cylinder. Secure the car in this posi- 
tion by passing a strong rope under the girdle or crosshead and 
over the sheave timbers. When secured, close the gate valve in 
the supply pipe, open the air cock at the head of the cylinder, and 
throw the operating valve for the car to go up. Also open the 
valve in the drain pipe from the side of the cylinder, and from 
the lower head of the cylinder, thus allowing the water to dram 



774 HANDBOOK ON ENGINEERING. 

out of the cylinder. When the cylinder is empty, throw the valve 
for the car to descend in order to drain the water from the cir- 
culating pipe. In case of tank pressure, where level of water in 
lower tank is above the bottom of the cylinder, the gate valve in 
the discharge pipe will have to be closed as soon as the water in 
the cylinder is on a level with that of the tank, allowing the rest 
to pass through the drain pipe to the sewer. When the water is 
all drained off, remove the lower head of the cylinder, and the 
piston will be accessible. Remove the bolts in the piston follower 
by means of the socket wrench, which is furnished for that pur- 
pose. Before removing the piston head, mark its exact position, 
then there will be no difficulty in replacing it ; also be careful and 
not let the piston get turned in the cylinder, so as to twist the 
piston rods. On removing the piston follower, you will find a 
leather cup turned upwards, with coils of § in. square duck 
packing on the outside. This you will remove and clean out the 
dirt ; also clean out the holes in the piston, through which the water 
acts upon the cups. If the leather cup is in good con- 
dition, replace it and on the outside place three new coils of 
| inch square duck packing, being careful that they break joints 
and also that the thickness of the three coils up and down does 
not fill the space by \ inch, as in such case the water might swell 
the packing sufficiently to cramp it in this space, thus destroying 
its power to expand. If too tight, strip off a few thicknesses of 
canvas. Replace the piston follower and cylinder head, and the 
cylinder is ready to refill. Close the valves in the drain pipes, 
leave the air cock open at the head of the cylinder and the oper- 
ating valve in the position to descend, and open gate valve in the 
discharge. Slowly open the gate valve in the supply pipe, allow- 
ing the cylinder to fill gradually and the air to escape at the head 
of the cylinder. When the cylinder is full of water, leave the air 
cock open and put the operating valve on the center. The car can 
then be untied, the stop button can be reset, and the elevator is 
ready to use. Make a few trips before closing the air valve. 



HANDBOOK ON ENGINEERING. 



775 




The above cut is the Auxiliary Valve for Crane Hydraulic 
Passenger Elevators. 

The operation of this valve is explained as follows : D repre- 
sents the supply inlet- E, the discharge outlet; F, the opening 



776 HANDBOOK ON ENGINEERING. 

to the cylinder ; G, the pilot valve ; If, the pilot valve supply 
pipe to" the motor cylinder ; N and J, the attachment by which 
the valve is operated. Fig. 1 represents the valve on centers, or 
the car at rest at any floor between limits of travel. It will be 
noticed in cut that the plunger heads A and B are on either side 
of the central opening. The water is then entirely cut off from 
the machine and the pilot valve covers the port C. To start the 
car up, water is admitted to the cylinder /through the inlet D. 
This is accomplished by pushing on the connection in which 
opens the port C in the pilot valve G, allowing the water in the 
motor cylinder I to flow into the discharge E. The flow is regu- 
lated by the screw K. The pressure in the motor cylinder I 
being relieved, the valve plunger moves to the right under the 
difference in pressure upon the plunger A and L, L being of 
smaller diameter than A. Supply is thus admitted to the cylin- 
der through F. To start the car down, pull on the connection J. 
The port C in the pilot valve chest is opened, allowing water 
from the pilot supply H to flow into the motor cylinder I. The 
pressure on head forces the plunger B to move to the left. Water 
is thus allowed to pass out from F to the discharge E. If a 
slow movement of the car is desired, connection J \s removed to 
the right or left for either up or down, and only enough to open 
the main valve slightly to give the desired speed. This speed is 
maintained by the lever being moved on its fulcrum P, thus 
necessitating the valve G covering port C. 

AUTOflATIC STOP VALVE. 

Trie stop valve M is opened automatically by the machine as 
the elevator starts from the top or bottom landing, giving free flow 
of water to the cylinder. As the car reaches the upper or lower 
limit of travel, the valve is automatically closed, so that the car 
stops gradually at the terminals. 



HANDBOOK ON ENGINEERING. . 777 

OTIS GRAVITY WEDGE SAFETY. 

J, Under the car is a heavy hardwood safety plank, on each 
1 end of which is an iron adjustable jaw, inclosing the guide on 
I the guide post. In this jaw is an iron wedge, withheld from con- 
tact with the guide in regular duty. Under the wedge is a rocker 
arm, or equalizing bar, with one of the lifting cables attached 
independently at each extremity. The four lifting cables, after 
being thus attached, pass over a wrought iron girdle at the top 
of the car. Each cable carries an equal strain, and the breakage 
of any one cable puts the load on the other cables, which throws 
the rocker out of equilibrium and forces the wedges on both sides 
instantly and immovably between the iron jaws of the safety 
plank and the side of the guides, stopping the car. It may be 
raised to any position by the unbroken cables, though it cannot 
be lowered until a new cable is put on. 

2* Any cable will always stretch before it breaks, which will 
throw the equalizing safety-bar out of equilibrium and force the 
wedges on both sides into position. No other safety device will 
give warning in advance. 

CARE OF HALE ELEVATORS. 

Keep the guide springs on the girdle above, and the safety 
plank below the car adjusted, so that the car will not wabble, but 
not tight enough to bind against guides. When cables are draw- 
ing alike, the equalizing bars on a passenger elevator should be 
horizontal, and the set screws free from contact with the finger 
shaft, but adjusted so that one of them will come in contact 
with the finger shaft when the equalizing bar is tipped a certain 
amount either way. If the safety wedges should be thrown in, 
or rattle, when descending, the cause would be from the stretch- 
ing or breaking of one of the cables, the action of the governor, 
or from weakness of either the spring on the finger shaft, 



778 HANDBOOK ON ENGINEERING. 

safety-wedge or gummy guides. In the first case, if occa 
sioned by the cable stretching, the cable should be examined 
thoroughly, and if it shows weakness, a new one put on, 
otherwise, it can be shortened up, as stated above. In the sec- 
ond case, the car had probably attained excessive speed and the 
governor simply performed its proper function. In the third 
case, new springs should be put on and the guides kept clean, . 
for it often happens that the guides are so dirty that the springs 
cannot well prevent the wedges catching. All the safeties shoutd 
be kept clean and in good order, so that they will quickly respond 
when called upon to perform their duty. To loosen the wedges 
when thrown in, throw the valve for the car to ascend. If the 
wedges are thrown in above the top landing, remove the button 
on the hand cable and run the car up until the piston strikes the 
bottom of the cylinder. If this is not sufficient to loosen the 
wedges, the car will have to be raised by a tackle. Keep all nuts 
properly tightened. 

If traveling- or auxiliary sheave bushing is worn so that sheave 
binds, or the bushing is nearly worn through, turn it half round, 
and thus obtain a new bearing. If it has been once turned put 
in a new bushing. See that the piston rods draw alike. If they 
do not, it can be discerned by trying to turn the rods with the 
hand, or by a groaning noise in the cylinder. However, this 
groaning may also be caused by the packing being worn out, in 
which case the car would not stand stationary. See that 'ail 
supports remain secure and in good condition. 

WATER FOR USE IN HYDRAULIC ELEVATORS. 

In hydraulic elevator service little heed is usually given to the 
quality of water with which the system is operated. Much loss 
of power by friction and many dollars spent annually in repairs 
can be avoided by a little thought and action on this subject. In 
order to prove the truth of this statement, one has only to obtain 



HANDBOOK ON ENGINEERING. 779 

two samples of water, one of soft water and the other of what is 
commonly known as hard water. For example, take rain water 
as the first sample and water from the well as the second. Now 
rub your hands briskly together while holding them immersed in 
one, and then in the other of these samples. You will instantly 
realize that the quality of water used in elevator service has much 
to do with the efficiency of the hydraulic machinery. Water from 
the service pipes of the city water-works always contains more or 
less sand and other gritty substances, in suspension, and this grit 
acts much the same on the packing and metal parts of the appar- 
atus as does a sand blast. Some engineers, having realized the 
evil effects of water in the state that it is generally used, have 
attempted to remedy the matter by replacing the water which is 
lost by leakage or evaporation by the addition of the water which 
is discharged from the steam traps of the plant ; and as this has 
been distilled, it is almost chemically pure — thus the man who 
uses distilled water in an elevator system instead of the water 
containing grit, is simply getting out of one difficulty into 
another. 

It is a well-known fact in chemistry that pure water is a solvent 
for every known substance, and will especially attack iron to a 
large degree. Whenever it is practicable, the water for elevator 
use should be passed through a filter to remove grit before 
being allowed to pass into the surge tank. In many cases, 
however, it would be difficult for the engineer to convince the 
owner of the advisability of buying and installing a filter for this 
purpose. A simple and somewhat inexpensive remedy is within 
reach of all — the plentiful use of soap will obviate many of the 
evil effects of hardness of the water, will double the life of the 
packing, will reduce the loss by friction, and will, to a large 
extent, prevent the chattering of the pistons, making the elevators 
run much smoother. In laboratory practice, the degree of hard- 
ness or softness of water is determined by the amount of pure 



780 



HANDBOOK ON ENGINEERING. 




HANDBOOK ON ENGINEERING. 781 

soap that is necessary to mix with the water to form a lather, or 
to precipitate a certain quantity of carbonate of lime and other 
substances. This same action, on a larger scale, takes place 
when soap is introduced into an elevator tank, and while the oily 
portion of the soap forms an emulsion with the water, of great 
lubricating properties, the gritty matter is precipitated and can 
be gotten rid of through means of a blow-off in the bottom of the 
tank. The cheapest and most convenient form in which to obtain 
soap for this purpose, is the soap powder extensively manufac- 
tured by various firms and which can be purchased for about four 
cents per pound. In a plant of six elevators, with usually a 
storage capacity of some 8,000 gallons, it is a good practice to 
use about twenty pounds of this soap each week. The soap 
should be at first dissolved in about ten times its weight of boil- 
ing water, and when cold it will form a stiff soft soap. The 
practice of putting in the refuse oil collected from the drip pans is 
of little value ; it will not mix with the water, but floats on the 
surface. It rarely gets low enough to enter the suction pipes of 
the pumps, and has little or no tendency to precipitate the solid 
matter that is held in suspension in the water. 

If car settles, the most probable cause is that the valve or pis- 
ton needs repacking. If packing is all right, then the air valve 
in the piston does not properly seat. If the car springs up and 
down when stopping, there is air in the cylinder. When there 
is not much air, it can often be let out by opening the air cock 
and running a few trips, but when there is considerable air, 
run the car to near the bottom, placing a block underneath for 
it to rest upon, then place the valve for the car to descend. 
While in this position, open the air cock and allow the air to 
escape. This may have to be repeated several times before the 
air is all removed. 

Keep the cylinder and connections protected from frost. 
Where exposed, the easiest way to protect the cylinder is by an 



782 HANDBOOK ON ENGINEERING. 

air-tight box, open at the bottom, at which point keep a gas jet 
burning during cold weather. Where there is steam in the build- 
ing, run a coil near the cylinder. Keep stop buttons on hand cable 
properly adjusted, so that the car will stop at a few inches beyond 
either landing, before the piston strikes the head of the cylinder. 
Regulate the speed desired for the car by adjusting the back stop 
buttons, so that the valve can only be opened either way suffi- 
ciently to give this speed. Occasionally try the governor to see 
that it works properly. Keep the machinery clean and in good 
order. 

ELEVATOR INCLOSURES AND THEIR CARE. 

Elevator inclosures, while intended for protection to passen- 
gers, are often carelessly neglected and are often a source of 
danger, unless looked after and taken care of in a proper manner. 
It is of the utmost importance that no projection of any kind 
shall extend into the doorways for clothing of passengers to 
catch on, thus endangering their lives. The door should move 
freely to insure their action at the touch of the operator. See 
that all bolts and screws are tight, and replace at once all that 
fall out, otherwise, the doors and panels may swing into the path 
of the elevator cage and be torn off, and probably injure some 
one, thus placing the owner liable to damages. Elevator doors 
that are automatic in their closing are the best, but all operators 
should be held strictly responsible for accidents occurring from 
the carelessness of leaving doors open. All inclosures should be 
equipped with aprons above the doors to the ceiling and as close 
to the cage as possible, to prevent passengers from falling out or 
extending their person through to be caught by ceilings or beams 
in the elevator shaft. As a rule, proprietors of buildings take a 
pride in keeping their inclosures and cars in a neat condition, as 
they are considered an ornament to the building for the purpose 
for which they are intended, and no expense is spared in the 



HANDBOOK ON ENGINEERING. 



783 



line of art; so it is recommended that they be kept free from 
dampness. Dust with a feather duster and use soft rags for 
cleaning. Never use any gritty substance, soaps or oils. If they 
become damaged, have the maker repair and relacquer them. 

STANDARD HOISTING ROPE WITH 19 WIRES 
TO THE STRAND. 



© 
H 


© 

I 

s 


1 

s a a 

5 * 


Weight per 
foot in lbs. 

of rope 
with hemp 

center. 


Breaking 
strain in 
tons of 
2000 lbs. 


Proper 

working 

load in tons 

of 

2000 lbs. 


Circumfer- 
ence of new 
Manilla 
rope of 
equal 
strength. 


Minimum 

size of 

drum or 

sheave in 

feet. 


1 


2* 


61 


8.00 


74 


15 


14 


13 


2 


2 


6 


6.30 


65 


13 


13 


12 


3 


U 


5ft 


5.25 


54 


11 


12 


10 


4 


If 


5 


4.10 


44 


9 


11 


8ft 


5 


ift 


41 


3.65 


39 


8 


10 


n 


5ft 


il 


4| 


3.00 


33 


6ft 


n. 


7 


6 


U 


4 


2.50 


27 


5ft 


8ft 


&ft 


7 


H 


8* 


2.00 


20 


4 


74 


6 


8 


l 


8* 


1.58 


16 


3 


6ft 


H 


9- 


i 


2| 


1.20 


11.50 


2ft 


5ft 


4ft 


10 


1 


24 


0.88 


8.64 


H 


41 


4 


10| 


1 


2 


0.66 


5.13 


n 


31 


u 


10ft 


9 
16 


If 


0.44 


4.27 


i 


3ft 


2| 


101 


ft 


1* 


0.35 


3.48 


& 


3 


24 


10a 


_1- 
1 6 


If 


0.29 


3.00 


i 


21 


2 


10i 


1 


H 


0.26 


2.50 


\ 


2ft 


1ft 



Operating Cable or Tiller Rope, f in. diaro. ; | in. diam. 
; in. diam. 



4 in. diam.; 



Cables, and how to care for them. — Wire and hemp ropes of 
same strength are equally pliable. Experience has demonstrated 
that the wear of wire cables increases with the speed. Hoisting- 
ropes are manufactured with hemp centers to make them more 
pliable. Durability is thereby increased where short bending 



784 HANDBOOK ON ENGINEERING. 

occurs. All twisting and kinking of wire rope should be avoided. 
Wire rope should be run off by rolling a coil over the ground 
like a wheel. In no case should galvanized rope be used for 
hoisting purposes. The coating of zinc wears off very quickly 
and corrosion proceeds with great rapidity. Hoisting cables 
should not be spliced under any circumstances. All fastenings 
at the ends of rope should be made very carefully, using only 
the best babbitt. All clevises and clips should fit the rope 
perfectly. Metal fastenings, where babbitt is used, should be 
warmed before pouring, to prevent chilling. Examine wire ropes 
frequently for broken wires. Wire hoisting ropes should be con- 
demned when the wires (not strands) commence cracking. Keep 
the tension on all cables alike. Adjust with draw-bars and turn- 
buckles provided. 

Leather cup packings for valves* — Leather for cups should 
be of the best quality, of an even thickness, free from blemish 
and treated with a water-proof dressing. The cups should be 
of sufficient stiffness to be self-sustaining when passing over per- 
forated valve lining When ordering cups, the pressure of water 
carried should be specified, as the stiff cups intended for high- 
pressure would not set out against the valve lining when low pres- 
sure is used. 

Water* — Water for use in hydraulic elevators should be per- 
fectly clear and free from sediment. A strainer should be placed 
on the supply pipe and water changed every three months, and 
the system washed and flushed. 

Closing" down elevators. — If an elevator is to be shut down 
for an indefinite period, run the car to the bottom and drain off 
the water from all parts of the machine ; otherwise, a freeze is 
likely to burst some part of the machinery. If the machine is of 
the horizontal type, grease the cylinder with a heavy grease ; if 
vertical, the rods should be greased. Oil cables with raw linseed 
oil. 



HANDBOOK ON ENGINEERING. 785 

LUBRICATION FOR HYDRAULIC ELEVATORS. 

The most effectual method of lubricating the internal parts of 
hydraulic elevator plants where pump and tanks are used, is to 
carry the exhaust steam drips from the foot of the pump exhaust 
pipe to the discharge tank, thus saving the distilled water and 
cylinder oil. This system is invaluable when water holding in 
solution minerals is used, as these minerals greatly increase cor- 
rosion. Horizontal machines operated by city pressure are best 
lubricated with a heavy grease applied either mechanically or by 
means of a piece of waste on the end of a pole. The former 
method serves as a constant lubricator, while in the latter case, 
greasing is often neglected, and in consequence packing lasts but 
a short time. 

Lubrication of worm gearing* — Oils with a body, such as 
cylinder and castor oils, are best suited to the purpose. A com- 
position of two parts castor to one part cylinder oil of the very 
best quality, makes a desirable lubricant, for the following rea- 
sons : cylinder oil being heavy with ample body, on becoming 
warm runs freely to the point of contact between the worm and 
the gear and lubricates readily. On the other hand, castor oil 
when cool, or only slightly warm, retains its body and makes an 
excellent lubricant. Upon becoming heated, castor oil thickens, 
thus rendering it objectionable. By the combination, efficient 
lubrication is obtained at all temperatures. 

Lubrication of cables* — A good compound for preservation 
and lubrication of cables is composed of the following : Cylinder 
oil, graphite, tallow and vegetable tar, heated and thoroughly 
mixed. Apply with a piece of sheepskin with wool inside. To 
prevent wire rope from rusting, apply raw linseed oil. 

Lubrication of guides* — Steel guides should be greased with 
good cylinder oil. Grease wood strips with No. 3 Albany grease 
or lard oil. Clean guides twice a month to prevent gumming. 

50 



786 HANDBOOK ON ENGINEERING. 

Lubrication of overhead sheave boxes* — In summer use a 
heavy grease. In winter, add cylinder oil as required. 

BELTS AND HOW TO CARE FOR THEM. 

The work required of an elevator belt is most severe and we 
might say extraordinary character, running as it does over a large 
to a small pulley and beneath an idler, so situated as to give the 
small pulley as much belt surface as possible. The belt runs 
forward and backward as the cage descends and ascends, thereby 
causing a certain amount of slip. It is imperative that a belt 
performing such service should be of the very best quality. The 
following are the specifications : The stock should be strictly 
pure oak-tanned, cut in such a manner that the center of the hide 
will form the center of the belt. Each piece should have all 
stretch thoroughly removed. The belt should be short lap, none 
of the pieces to exceed 4' 2" in length, including the laps. Lock 
lap should be made, which makes a perfect splice. Under no 
circumstances should a straight lap be used. The cement should 
be of the very best quality and pliable to such an extent that it 
will allow for the short turn taken by the belt in passing under 
the idler and around the small pulley. As a precaution against 
laps coming apart from accident or other cause, belts should be 
riveted, as the rivets will hold lap together until defect may be 
seen and remedied. Owing to the high speed, laced belts should 
never be used, as the laces are sure to be cut by running over the 
small pulleys. Castor oil makes a very reliable dressing for 
belts. It renders them pliable, thus improving the adhesive 
qualities. 

USEFUL INFORMATION. 

To find leaks in elevator pressure tanks in which air is con- 
fined, paint round the rivet heads with a solution of soap and the 
leak will be found wherever a bubble or suds appear. To ascer- 
tain the number of gallons in cylinders and round tanks, multi- 



HANDBOOK ON ENGINEERING. 



787 



ply the square of the diameter in inches by the height in inches 
ply the square of the diameter in inches by the height in inches 
and the product by .0034 = gallons. Weight of round wrought 
iron : Multiply the diameter by 4, square the product and divide 
by 6 = the weight in pounds per foot. To find the weight of a 
casting from the weight of a pine pattern, multiply one pound of 
pattern by 16.7, for cast-iron, and by 19 for brass. Ordinary 
gray iron castings = about 4 cubic inches to the pound. 

Water* — A gallon of water (U. S. Standard) contains 231 
cu. in. and weighs 8-J- lbs. A cubic foot of water contains 7 J gal- 
or 1728 cu. in. and weighs 62.425 lbs. A " Miner's inch" is a 
measure for the flow of water and is the amount discharged 
through an opening 1 inch square in a plank 2 in. in thickness, 
under a head of 6 in. to the upper edge of the opening ; and this 
is equal to 11.625 U. S. gal. per minute. The height of a 
column of fresh water, equal to a pressure of 1 lb. per sq. in., is 
2.304 feet. A column of water 1 ft. high exerts a pressure of .433 
lbs. per sq. in. The capacity of a cylinder in gallons is equal to 
the length in inches multiplied by the area in inches, divided by 
231 (the cubical contents of one U. S. gal. in inches). The 
velocity in feet per minute, necessary to discharge a given volume 
of water in a given time, is found by multiplying the number of 
cu. ft. of water by 144 and dividing the product by the area of 
the pipe in inches. 



Decimal Equivalents of an Inch. 



1-16 


1-8 


3-16 


1-4 


5-16 


3-8 


7-16 


1-2 


.0625 


.125 


.1875 


.25 


.3125 


.375 


.4375 


.5 


9-16 


5-8 


11-16 


3-4 


13-16 


7-8 


15-16 




.5625 


.625 


.6875 


.75 


.8125 


.875 


.9375 





788 HANDBOOK ON ENGINEERING. 



CHAPTER XXVII. 

THE DRIVING POWER OF BELTS. 

The average strain or tension at which belting should be run, 
is claimed to be 55 pounds for every inch in width of a single belt, 
and the estimated grip is one-half pound for every square inch of 
contact with pulley, when touching one-half of the circumference 
of the pulley. For instance a belt running around a 3 6 -inch pul- 
ley would come in contact with one-half its circumference, or 561 
inches, and allowing a half-pound per inch, would have a grip 28 J 
pounds for each inch of width of belt. 

flECHANICAL PROBLEMS AND RULES. 

Problem 1. To find the circumference of a circle or a 
pulley : — 

Solution. Multiply the diameter by 3.1416 ; or, as 7 is to 22 
so is the diameter to the circumference. 

Problem 2. To compute the diameter of a circle or pulley: — 

Solution. Divide the circumference by 3.1416 ; or multiply 
the circumference by .3183 ; or as 22 is to 7, so is the circumfer- 
ence to the diameter, equally applicable to a train of pulleys, the 
given elements being the diameter and the circumference. 

Problem 3. To find the number of revolutions of driven pulley, 
the revolution of driver, and diameter of driver and driven being 
given : — 

Solution. Multiply the revolutions of driver by its diameter, 
and divide the product by the diameter of driven. 



HANDBOOK ON ENGINEERING. 789 

Problem 4. To compute the diameter of driven pulley for any 
desired number of revolutions, the size and velocity of driver 
being known : — 

Solution. Multiply the velocity of driver by its diameter and 
divide the product by the number of revolutions it is desired the 
driven shall make. 

Problem 5. To ascertain diameter of driving pulley : — 

Solution. Multiply the diameter of driven by the number of 
revolutions you desire it shall make, and divide the product by 
the number of revolutions of the driver. 

6. Rule for finding length of belt wanted: Add the diame- 
ters of the two pulleys together, divide the result by two, and 
multiply the quotient by 3 1/7. Add the product to twice the 
distance between the centers of the shafts, and you have the 
length required. 

For Calculating the Number of Horse-Power Which a Belt 
Will Transmit, Its Velocity and the Number of Square Inches 
in Contact With the Pulley Being Known. 

Divide the number of square inches of belt in contact with the 
pulley by two, multiply this quotient by velocity of the belt in 
feet per minute and divide the product by 33,000 ; the quotient is 
the number of horse-power. 

Example. — A 20-inch belt is being moved with a velocity of 
2,000 feet per minute, with six feet of its length in contact 
with the circumference of a four-foot drum ; desired its horse- 
power. 20 x 72 equal 1,440, divided by two, equals 720 x 2,000 
equal 1,440,000 divided by 33,000 equal 43| horse-power. 

Rule for finding width of belt, when speed of belt in feet per 
minute and horse power wanted are given : — 

For single belts* — Divide the speed of belt by 800. The horse- 
power wanted divided by this quotient, will /give^ the width of 
belt required. 



790 HANDBOOK ON ENGINEERING. 

Example. — Required the width of single belt to transmit 100 
horse-power. Engine pulley .72" in diameter. Speed of engine, 
220 revolutions per minute. 

800) 4146 (speed of belt per minute). 

5.18)100.00 (horse-power wanted). 

19" width of belt required. 

For double belts* — Divide the speed of belt in feet per minute 
by 560. Divide the horse-power wanted by this quotient for the 
width of belt required. 

Example. — Required the width of double belt to transmit 500 
horse-power. Engine pulley 72" in diameter. Speed of engine, 
220 revolutions per minute. 

560)4146 (speed of belt per minute). 

7.4)500.00 (horse-power wanted). 

67i" width of belt required. 

EXTRACTS FROM ARTICLES ON BELTS. 

BY R. J. ABERNATHEY. 

Although there is not near as much known in general about 
the power of transmitting agencies as there should be, still it 
seems that almost any other method or means is better understood 
than belts. 

One of the chief difficulties in the way of a better knowledge of 
the belting problem, is the relation that belts and pulleys bear to 
each other. The general supposition, and one that leads to many 
errors, is that the larger in diameter a pulley is, the greater its 
holding capacity — the belt will not slip so easily, is the belief. 
But it is merely a belief, and has nothing to sustain it, unless it 
be faith, and faith without work is an uncertain factor. I would 



HANDBOOK ON ENGINEERING. 791 

like here to impress upon the minds of all interested, the following 
immutable principles or law :. — 

1 . The adhesion of the belt to the pulley is the same — the arc 
or number of degrees of contact, aggregate tension or weight 
being the same — without reference to width of belt or diameter 
of pulley. 

2. A belt will slip just as readily on a pulley four feet in diam- 
eter, as it will on a pulley two feet in diameter, provided the 
conditions of the faces of the pulleys, the arc of contact, the ten- 
sion, and the number of feet the belt travels per minute are the 
same in both cases. 

3. A belt of a given width and making two thousand, or any 
other given number of feet per minute, will transmit as much 
power running on pulleys two feet in diameter as it will on 
pulleys four feet in diameter, provided the arc of contact, tension 
and conditions of pulley faces all be the same in both cases. 

It must be remembered, in reference to the first rule, that when 
speaking of tensions, that aggregate tension is never meant unless 
so specified. A belt six inches wide, with the same tension, or 
as taut as a belt one inch wide, would have six times the aggre- 
gate tension of the one inch belt. Or it would take six times 
the force to slip the six inch belt as it w r ould the one inch. I 
prefer to make the readers of this, practical students. I want 
them to learn for themselves. Information obtained in that way 
is far more valuable, and liable to last much longer. 

In order that the reader may more fully understand whether 
or not a large pulley will hold better than a small one, let him 
provide a short, stout shaft, say three or four feet long and two 
inches in diameter. To this shaft firmly fasten a pulley, say 
12 in. in diameter, or any other size small pulley that may be 
convenient. The shaft must then be raised a few feet from the 
floor and firmly fastened, either in vices, or by some other means, 
so that it will not turn. It would be better, of course, to have 



792 HANDBOOK ON ENGINEERING. 

a smooth-faced iron pulley, as such are most generally used. So 
far as the experiment is concerned, it would make no difference 
what kind of a pulley was used, provided all the pulleys experi- 
mented with be of the same kind, and have the same kind of face 
finish. When the shaft and pulleys are fixed in place, procure a 
new leather belt and throw it over the pulley. To one end of the 
belt attach a weight, equal, say, to forty pounds — or heavier, if 
desired — for each inch in width of belt used ; let the weight 
rest on the floor. To the other end of the belt attach another 
weight, and keep adding to it until the belt slips and raises the 
first weight from the floor. After the experimenter is satisfied 
with placing with the 12 in. pulley, he can take it off the 
shaft and put on a 24 in., a 36 in., or any other size he may 
wish ; or, what is better, he can have all on the shaft at the 
same time. The belt can then be thrown over the large pulley 
and the experiment repeated. It will then be found if pulley 
faces are alike, that the weight which slipped the belt on the 
small pulley will also slip it on the large one. The method 
shows the adhesion of a belt with 180 degrees contact, but as the 
contact varies greatly in practice, it is well enough to understand 
what may be accomplished with other arcs of contact. But, after 
all, many are probably at a loss how to account for some obser- 
vations previously made. They have noticed that when a belt at 
actual work slipped, an increase in the size (diameter) of the 
pulleys remedied the difficulty and prevented the slipping. 

A belt has been known to refuse to do the work allotted to it, 
and continue to slip over pulleys two feet in diameter, but from 
the moment pulleys were changed to three feet in diameter there 
was no further trouble. These observed facts seem to be at 
variance with and to contradict the results of the experiments 
that have been made. All, however, may rest assured that it is 
only apparent, not real. 

The resistance to slippage is simply a unit of useful effect (or 



HANDBOOK ON ENGINEERING. 793 

that which can be converted into useful effect) . The magnitude 
of the unit is in proportion to the tension of the belt. The sum 
total of useful effect depends upon the number of times the unit 
is multiplied. A belt 6 inches wide and having a tension equal 
to 40 lbs. per inch in width, and traveling at the rate of 1 foot 
per minute, will raise a weight of 240 lbs. 1 foot high per minute. 
If the speed of the belt be increased to 136.5 feet per minute, it 
will raise a weight of 33,000 lbs. per minute, or be transmitting 
1 horse-power. The unit of power transmitted by a belt is rather 
more than its tension, but to take it at its measured tension is at 
all times safe, and 40 to 45 lbs. of a continuous working strain is 
as much, perhaps, as a single belt should be subjected to. A 
little reflection will now convince the reader that a belt transmits 
power in proportion to its lineal speed, without reference to the 
diameter of the pulleys. Having arrived at that conclusion, it is 
then easy to understand why it is that a belt working over 36-inch 
pulley will do its work easy, when it refused to do it and slipped 
on 24-inch pulleys. If the belt traveled 800 feet per minute on 
the 24-inch pulleys, on the 36-inch it would travel 1,200 feet, 
thus giving it one-half more transmitting power. If, in the first 
instance, it was able to transmit but 8 horse-power, in the second 
instance it will transmit 12 horse-power. All of which is due to 
the increase in the speed of the belt and not to the increase in the 
size of the pulleys ; because, as has been shown, the co-efficient 
of friction, or resistance to slippage, is the same on all pulleys 
with the same arc of belt contact. 

There is no occasion for elaborate and perplexing formulas and 
intricate rules. They serve no useful purpose, but tend only to 
mystify and puzzle the brain of all who are not familiar with the 
higher branches of mathematics, — and it is the fewest number 
of our every-day practical mechanics who are so familiar. In all, 
or nearly all treatises on belting, the writer will tell you that at 
600, 800 or 1,000 feet per minute, as the case may be, a belt one 



794 HANDBOOK ON ENGINEERING. 

inch wide, will transmit one horse-power ; and yet, when we come 
to apply their rules in practice, no such results can be obtained 
one time in ten. The rules are just as liable to make the belt 
travel 400, 1,000 or 1,600 per minute per horse-power as the 
number of feet they may give as indicating a horse-power. 

I have adopted, and all my calculations are based upon the 
assumption that a belt traveling 800 feet per minute, and running 
over pulleys, both of which are the same diameters, will easily 
transmit one horse-power for each inch in width of belt. A belt 
under such circumstances would have 180 degrees of contact on 
both pulleys without the interposition of idlers or tighteners. 

The last proposition being accepted as true and the basis cor- 
rect, the whole matter resolves itself into a very simple problem, 
so far as a belt with 180 degrees contact is concerned. It is 
simply this: If a belt traveling 800 feet per minute transmit one 
horse-power, at 1,600 feet, it will transmit two horse-power ; or 
if 2,400 feet, three horse-power, and so on. It is no trouble for 
any one to understand that, if he understands simple multiplica- 
tion or division. 

It is not, however, always the case that both pulleys are the 
same size, and as soon as the relative sizes of the pulleys change, 
the transmitting power of the belt changes ; and that is the rea- 
son why no general rule has ever, or ever will be made for ascer- 
taining the transmitting capacity of belts under all circumstances. 
When the pulleys differ in size, the larger of the two is lost sight 
of — it no longer figures in the calculations — the small pulley, 
only, must be considered. To get at it, the number of degrees 
of belt contact on the small pulley must be ascertained as nearly 
as possible and use for a guide, for getting at the transmitting 
power, the next established basis below. Of course, the experi- 
menter can make a rule for every degree of variation, but it would 
require a great many, and is not necessary. I use five divisions, 
as follows : — 



HANDBOOK ON ENGINEERING. 795 

For 180 degrees useful effect .... 100 

For 1571 " " " 92 

For 135 " " " 84 

For 112i " " " .... .76 

For 1)0 " " " 64 

The experimenters may find that my figures are under obtained 
results, which is exactly what they are intended to be, more 
especially at the 90 degree basis. I wish to make ample allow- 
ance. 

To ascertain the power a belt will transmit under the first-named 
conditions : Divide the speed of the belt in feet per minute by 
800, multiply by its width in inches and by 100. For the second, 
divide by 800, multiply by width in inches and by .92. Third 
place, divide by 800, multiply by width in inches and by .84. 
Fourth place, divide by 800, multiply by width in inches and by 
.76. Fifth place, divide by 800, multiply by width in inches and 
by .64. As an example: What would be the transmitting power 
of a 16-inch belt traveling 2,500 feet per minute by each of the 
above rules ? 

1st: 2,500 divided by 800 equal 3.125x 16 & 100 equal 50 h. p. 

3.125x 16 & .92 equal 46 " 
3.125x 16 & .84 equal 42 " 
3.125x16 & .76 equal 38 " 
3.125 x 16 & .64 equal 32 " 

As I have said, if the degrees of contact come between the 
divisions named above, in order to be on the safe side, calculate 
from the first rule below it, or make an approximate as you like. 

If the above lesson is studied well and strictly used, there can 
be no excuse for any mechanic putting in a belt too small for the 
work it has to do, provided he knows how much there is to do, 
which he ought, somewhere near at least. 



2d: 


2,500 


800 


3d: 


2,500 


800 


4th: 


2,500 


800 


5th: 


2,500 


800 



796 



HANDBOOK ON ENGINEERING. 



HORSE-POWER TRANSMITTED BY LEATHER 
BELTS. 

DRIVING POWER OF SINGLE BELTS. 



Speed in 






Width of 


Belt in Inches. 






Feet per 






































Minute. 


2 


3 


4 


5 


6 


8 


10 


12 


14 




H. P. 


H. P. 


H. P. 


H. P. 


H. P. 


H. P. 


H. P. 


H. P. 


H. P. 


400 


1 


1* 


2 


2\ 


3 


4 


5 


6 


7 


600 


1* 


n 


3 


3| 


4i 


6 


n 


9 


10* 


800 


2 


3 


4 


5 


6 


8 


10 


12 


14 


1,000 


n 


8| 


5 


6* 


71 


10 


m, 


15 


171 


1,200 


3 


4+ 


7 


71 


9 


12 


15 


18 


21 


1,500 


3| 


fit 


?! 


9* 


11* 


15 


18| 


22* 


26* 


1,800 


4* 


«* 


9 


114 


13* 


18 


221 


27 


31* 


2,000 


5 


n 


10 


121 


15 


20 


25 


30 


35 


2,400 


6 


9 


12 


15 


18 


24 


30 


36 


42 


2,800 


7 


10* 


14 


m 


21 


28 


35 


42 


49 


3,000 


n 


U* 


15 


18| 


221 


30 


371 


45 


52* 


3,500 


81 


13 


17* 


22 


26 


35 


44 


52* 


61 


4,000 


10 


15 


20 


25 


30 


40 


50 


60 


70 


4,500 


Hi 


17 


22| 


28 


34 


45 


57 


69 


78 


5,000 


m 


19 


25 


31 


371 


50 


62* 


75 


87 



DRIVING POWER OF DOUBLE BELTS. 



Speed in 
Feet per 






Width of 


Belts in Inches. 
























Minute. 


6 


8 


10 


12 


14 


16 


18 


20 


24 




H. P. 


H. P. 


H. P. 


H. P 


H. P. 


H. P. 


H. P. 


H. P 


H. P. 


400 


44 


51 


74 


8* 


10 


11* 


13 


14* 


17* 


600 


6* 


81 


11 


13 


15 


17* 


19* 


22 


26 


800 


8* 


11* 


14* 


17* 


20* 


23 


26 


29 


34* 


1,000 


11 


1** 


184 


21* 


25* 


29 


32* 


36 


43* 


1,200 


13 


17* 


22 


26 


30* 


34* 


39 


44 


52* 


1,500 


164 


21| 


274 


32* 


38 


43* 


49 


54* 


65* 


1,800 


19* 


26 


32| 


39 


45* 


52 


59 


65£ 


78* 


2,000 


21| 


29 


36* 


43* 


50* 


58 


65* 


72* 


87 


2,400 


26 


34| 


44 


52* 


60* 


69* 


78* 


88 


105 


2 800 


301 


401 


51 


61 


71 


81 


91* 


102 


122 


3,000 


32* 


43* 


54* 
63* 


65* 


76 


87* 


98 


108 


131 


3,500 


38 


50| 


76 


89 


101 


114 


127 


153 


4,000 


43* 


584 


72i| 


87 


101 


116 


131 


145 


174 


4,500 


49 


65 


82 


98 


114 


131 


147 


163 


196 


5,000 


54* 


72| 


91 


109 


127 


145 


163 


182 


218 



HANDBOOK ON ENGINEERING. 797 

Example. — Required the width of a single belt, the velocity of 
which is to be 1,500 feet per minute ; it has to transmit 10 horse- 
power, the diameter of the smaller drum being four feet with live 
feet of its circumference in contact with the belt. 

33,000 x 10 equal 330,000, divided by 1,500 equal 220, divided 
by 5 equal 44, divided by 6 equal 1\ inches, the required width of 
belt. 

Directions for calculating the number of horse power which a 
belt will transmit. Divide the number of square inches of belt in 
contact with the pulley by two ; multiply this quotient by the 
velocity of the belt in feet per minute ; again we divide the total 
by 33,000 and the quotient is the mumber of horse-power. 

Explanations. — The early division by two is to obtain the 
number of pounds raised one foot high per minute, half a pound 
being allowed to each square inch of belting in contact with the 
pulley. 

Example. — A six-inch single belt is being moved with a 
velocity of 1,200 feet per minute, with four feet of its length in 
contact with a three-foot drum. Required the horse-power. 

6x48 equal 288, divided by 2 equal 144 x 1,200 equal 172,- 
800, divided by 33,000 equal, say, 5J horse-power. 

It is safe to reckon that a double belt will do half as much 
work again as a single one. 

Hints to users of belts. — 1. Horizontal, inclined and long 
belts give a much better effect than vertical and short belts. 

2. Short belts require to be tighter than long ones. A long 
belt working horizontally increases the grip by its own weight. 

3. If there is too great a distance between the pulleys, the 
weight of the belt will produce a heavy sag, drawing so hard on 
the shaft as to cause great friction at the bearings ; while, at the 
same time, the belt will have an unsteady motion, injurious to 
itself and to the machinery. 

4. Care should be taken to let the belts run free and easy, so 



798 HANDBOOK ON ENGINEERING. 

as to prevent the tearing out of the lace holes at the lap ; it also 
prevents the rapid wear of the metal bearings. 

5. It is asserted that the grain side of a belt put next to the 
pulley will drive 30 per cent more than the flesh side. 

6. To obtain a greater amount of power from the belts the pul- 
leys may be covered with leather ; this will allow the belts to run 
very slack and give 25 per cent more durability. 

7 . Leather belts should be well protected against water and even 
loose steam and other moisture. 

8. In putting on a belt, be sure that the joints run with the 
pulleys, and not against them out. 

9. In punching a belt for lacing, it is desirable to use an oval 
punch, the larger diameter of the punch being parallel with the 
belt, so as to cut out as little of the effective section of the leather 
as possible. 

10. Begin to lace in the center of the belt and take care to keep 
the ends exactly in line and to lace both sides with equal tight- 
ness. The lacing should not be crossed on the side of the belt that 
runs next the pulley. Thin but strong laces only should be used. 

11. It is desirable to locate the shafting and machinery so that 
belts shall run off from each other in opposite directions, as this 
arrangement will relieve the bearings from the friction that would 
result where the belts all pull one way on the shaft. 

12. If possible, the machinery should be so planned that the 
direction of the belt motion shall be from the top of the driving to 
the top of the driven pulley. 

13. Never overload a belt. 

14. A careful attention will make a belt last many years, which 
through neglect might not last one. 

DIRECTIONS FOR ADJUSTINC BELTING. 

In lacing cut the ends perfectly square, else the belt will 
stretch unevenly. Make two rows of holes in each end ; put the 



HANDBOOK ON ENGINEERING. 



799 



ends together and lace with lace leather, as shown in the cuts 
below. For wide belts, in addition, put a thin piece of leather or 




llllllliilr iiiiiiiiiiiiiiiiiiffl! 

rubber on the back to strengthen the joint, equal in length to the 
width of the belt, and sew or rivet it to the belt. In putting on 
belting, it should be stretched as tight as possible, and with wide 
belts, this can be done best by the use of belt clamps. 



HORSE POWER OF BELTING. 

To ascertain horse-power which belts will transmit, multiply 
width of belt by diameter of pulley (in inches), by revolutions 
of pulley (per minute), by number in table (corresponding to the 
pull the belt can exert per inch of width). 

Example. — 10" single horizontal belt, 36" pulley, 200 revolu- 
tions, pull taken at 50 lbs. 

10" x 36" x 200 x 0.0004 = 28.8 horse-power. 

The pulls which belts 1" wide will transmit are as follows : — 
Single horizontal belts (pulleys nearly same diameter) 50 lbs. 
Double " " " " li 

Single vertical u ;t " " 

Double " i; " ' 4 " 

Single belts (large to very small pulleys) 
Double " " " u ... 



100 
40 
60 
10 
15 
Quarter twist, single belts .25 



double 



40 



800 HANDBOOK ON ENGINEERING 



CHAPTER XXVIII. 

[CAPACITY OF AIR COHPRESSORS. 

To ascertain the capacity of an air compressor in cubic feet of 
free air per minute, the common practice is to multiply the area 
of the intake cylinder by the feet of piston travel per minute. 
The free air capacity of the compressor, divided by the number 
of atmospheres, will give the volume of compressed air per 
minute. To ascertain the number of atmospheres at any given 
pressure, add 15 lbs. to the gauge pressure ; divide this sum by 
15 and the result will be the number of atmospheres. The above 
method of calculation, however, is only theoretical and these 
results are never obtained in actual practice, even with com- 
pressors of the very best design working under the most favor- 
able conditions obtainable. Allowances should be made for 
losses of various kinds, the principal losses being due to clear- 
ance spaces, but in machines of poor design and construction 
other losses occur through imperfect cooling, leakages past the 
piston and through the discharge valves, insufficient area and 
improper working of inlet valves, etc. The writer has seen com- 
pressors where losses through imperfections and improper working 
conditions ranged from 15 to 25 per cent, while under favorable 
conditions and with the average compressor, the loss averages 
from 8 to 12 per cent. So that to get sufficiently accurate 
results in finding capacity of the compressor, subtract 12 per 
cent from above computation, which gives nearly accurate 
figures. The following table will be found useful for quickly 
ascertaining the capacity of an air compressor, also to find the 
cubical contents of any cylinder, receiver, etc. The first column 



HANDBOOK ON ENGINEERING. 



801 



is the diam. of cylinder in inches. The second shows the cubical 
contents in feet, for each foot in length. 

Contents of a Cylinder in Cubic Feet for Each Foot 
in Length. 





03 




d 03 


.2 a 


a as 




3 a 


S-O 


OS 


o § 


Q^ 




o 




1 


.0055 


6 


H 


.0085 


64 


h 


.0123 


64 


11 


.0168 


61 


2 


.0218 


7 


H 


.0276 


n 


n, 


.0341 


n, 


n 


.0413 


n 


3 


.0401 


8 


u 


.05 76 


84 


34 


.0668 


84 


m 


• 07<i7 


85 


4 


.0873 


9 


H 


.0985 


94 


44 


.1105 


9* 


45 


.1231 


n 


5 


.1364 


10 


H 


.1503 


10i 


54 


.1650 


10* 


51 


.1803 


10| 



OS 



.1963 
.2130 
.2305 
.2485 
.2673 
.2868 
.3068 
.3275 
.3490 
.3713 
.3940 
.4175 
.4418 
.4668 
.4923 
.5185 
.5455 
.5730 
.6013 
.6303 



.s-g 



11 

1H 

Hi 

m 

12 

12i 

13 

134 

14 

144 

15 

15* 

16 

16i 

17 

17^ 

18 

184 

19 

194 



03 

O o 
O 



.6600 
.6903 
• 721b 
.7530 
.7854 
.8523 
.9218 
.9940 
1.069 
1.147 
1.227 
1.310 
1.396 
1.485 
1.576 
1.670 
1.767 
1.867 
1.969 
2.074 



51 



20 

204 

21 

214 

22 

224 

23 

234 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

35 



CO 

o § 
O 


il 


2.182 


36 


2.292 


37 


2.405 


38 


2.521 


39 


2.640 


40 


2.761 


41 


2.885 


42 


2.885 


43 


3.012 


44 


3.142 


45 


3.400 


46 


3.687 


47 


3.976 


48 


4.587 




4.909 




5.241 




5.585 




5.940 




6.305 




6.681 





OS 

D 



7.069 

7.468 

7.886 

8.296 

8.728 

9.168 

9.620 

10.084 

10.560 

11.044 

11.540 

12.048 

12.566 



To find the capacity of an air-cylinder, multiply the figures in 
the second column by the piston travel in feet per minute. This 
applies to double-acting air cylinders. In the case of single- 
acting air cylinders, the result should be divided by 2. 



THE McKIERMAN DRILL COMPANY'S AIR COflPRESSOR. 

The air-cylinder and water-jacket are one complete casting. 

The heads are made with hoods and provision made for cool air 

in- take. 

51 



802 



HANDBOOK ON ENGINEERING. 



The atmosphere valves are bronze, of poppet form. There- 
fore, there is no vacuum and the cylinder fills absolutely with free 
air. The valves are closed by mechanical means. 

The discharge valves are self-acting, are made of bronze. All 
of them are free to inspection without removal or disturbance of 
other parts. 

The cooling apparatus, or heat-preventing device, is extremely 
effective. Water jacket completely surrounds the cylinder, water 




is forced to wash the walls and is kept in rapid motion from bot- 
tom to top, from end to end, absorbing heat rapidly. It filters 
the jacket at bottom, flows from end to end, around partitions, 
back and forth and up. Follows natural laws in absorbing, 
retaining and dispelling the heat of air. 

Regulation of pressure and speed is entirely automatic. The 
regulating device is the only one by which the air weighs the 
steam admitted to the cylinder. Throttle may be thrown wide 
open at start, then the regulator takes absolute control, governing 
the speed from highest to lowest rate, varying the speed for 



HANDBOOK ON ENGINEERING. 



803 



variable amounts of air which may be required and in such man- 
ner as to keep the pressure constant. 





fi ll 






The Bennett Automatic Air Compressor. 




-Z'^ "Z-L 



Ingersoll-Sergeant Air Compressor. 



804 HANDBOOK ON ENGINEERING. 

INGERSOLL=SERGEANT AIR COMPRESSOR, 

This engine, a cut of which is shown above, is fitted with Xn- 
gersoll-Sergeant Air Compressor Cylinders, and in connection 
with the Pohle Air Lift System, has double the supply of water, 
using only one-half the fuel previously required. The steam 
cylinders are of the Duplex Corliss condensing type and con- 
necting tandem, and on each side are two Ingersoll-Sergeant Air 
Cylinders and two Conover Water Cylinders. When the engine 




SECTIONAL VIEW OF AIR CYLINDER WITH VERTICAL LIFT VALVES. USED 
CLASS "E" AND "F" COMPRESSORS. 



is in operation, the air cylinders raise the water by the Pohle Air 
Lift System, from the wells to a tank at the surface, and from 
there it is taken by the water cylinders and forced to the stand- 
pipe. The cost of this combination compares favorably with the 
old plan of using separate compressors and water pumps, each 
with their own steam cylinders, and the saving in attendance, 
friction and foundation commends its use. The engines run at a 
fixed moderate speed and the regulation of the air and water is 
effected by passing the water from suction to discharge when the 
tank is too low and by mechanically unloading the air cylinders 



HANDBOOK ON ENGINEERING. 805 

with a pressure regulator when the tank is too full. The regula- 
tion is cbne mechanically, with floats at the top and bottom of the 
receiving tank. This combination can also be furnished with 
Straight Line Compressors ; the advantage of the Duplex is that 
should it be necessary, the one side of the engine can be discon- 
nected and the other side made to do the work. 

As will be seen, the inlet valves which are on the lower side of 
the cylinder are offset, thus preventing their being sucked into 
the cylinder and wrecking the compressor. They are made out 
oi a solid piece of steel and are extremely durable, because they 
are placed vertically, work in a bath of oil and do not slide on 
their seats. Both the inlet and discharge valves, being in 
the cylinder, allow the heads to be thoroughly water-jacketed, 
and this is an important feature when it is remembered that 
the heat of compression is greatest at the end of the stroke. 
The cylinder is, therefore, completely water-jacketed. The 
valves are arranged so that the air can be taken from outside of 
the engine room, which increases the efficiency of the machine 8 
to 15 percent, and are easily accessible. 

The two inlet valves are located in the piston, and, with 
the tube, are carried back and forth with the piston. The valve 
on that face of the piston which is toward the direction of move- 
ment is closed, while the one on the other face is open. This is 
exactly as it should be in order to force out the compressed air 
from one end of the cylinder while taking in the free air at the 
other ; when the piston has reached the end of its travel there is, 
of course, a complete stop while the engine is passing the center, 
and an immediate start in the other direction. The valve which 
was open immediately closes . There is no reason for its remain- 
ing open any longer, and it closes at exactly the right time, its 
own weight being all that is necessary to move it. The valve 
on the other side is left behind by the piston and the free air 
is admitted to that end of the cylinder for compression: on the 



806 



HANDBOOK ON ENGINEERING. 



return stroke. No springs are used, and there is none of the 
throttling of the incoming air, and none of the clattering or 
hammering so noticeable with poppet-valves. As there is nothing 
to make the valve move faster than the piston, it stays behind until 
the piston stops, leaving the port wide open for the admission 




DETAILS OF PISTON INLET AIR CYLINDER. 

A.— Circulating Water Inlet. D.— Oil Hole for Automatic Oil Cup. G.— Piston Inlet Valv " 
B.— Circulating Water Outlet. E— Air Inlet (through piston inlet pipe). H.— Discharge Valva 
C.-Water Jacket Drain Pipe. F.— Air Discharge (showing flange). J.— Water Jacket. 

Sectional Cut of Ingersoll & Sargeant Single Compressor. 



of air. It is well known that while the fly-wheel and, of course, 
the crank, rotate at a uniform speed, the movement of the piston 
is not uniform, but gradually increases in speed from the start 
till the crank has reached half -stroke, when it gradually slows up 
till the crank is on the center, and at this moment of full stop 
the valve gently slides to its seat. 



HANDBOOK ON ENGINEERING. 



807 




The above is what is called the Pohle Air Lift 
System. 



808 HANDBOOK ON ENGINEERING. 

The illustrations on page 807 shows the method of pumping 
water by air. A compressor in connection with the air-lift sys- 
tem of pumping water by direct air pressure. The pump con- 
sists of a water pipe and an air pipe, the latter discharging the 
air into the former at its bottom, through a specially designed 
foot-piece. The natural levity of the air compared with the 
water, causes it to rise and, in rising, to carry the water with it 
in the form of successive pistons, following one another. This 
system of pumping has found a large range of application and is 
of peculiar service in connection with deep well pumping. For 
this purpose, the absence of mechanical parts many feet below 
the surface, offers a commanding advantage. Method No. 1 and 
No. 2 is almost alike, consisting of placing the air and water 
pipes alongside of one another in the well, connecting them at 
the bottom with an end piece. Method No. 3 consists of placing 
a water discharge pipe into the well ; the air passing down into 
the well through the annular space between the well casing and 
the water pipe. Method No. 4 consists in using the well casing 
as the water discharge pipe, and simply putting an air pipe down 
into the well, with a specially designed foot-piece attached at the 
bottom through which the air escapes. 



HANDBOOK ON ENGINEERING. 809 

CHAPTER XXVIII. — Continued. 
THE METRIC SYSTEM. 

It frequently happens that an engineer, in reading books and 
papers devoted to steam engineering, is confronted with terms 
taken from the metric system, which he does not understand. 
I give below a few of the metric system terms most commonly 
used, with their values in feet and inches, also, gallons, quarts, 
pounds, tons, etc. 

A French meter is 30.37079 inches long, or a little less than 
39f inches. It is generally taken, — for convenience in fig- 
uring, — at 39.37 inches. 

1 decimeter is T ^ of a meter, or, 3.937 inches nearly. 

1 centimeter is -j-J^ " " " .3937 " " 

1 millimeter is j-Jqq- " " " .03937 " " 



1 decameter equals 10 meters, or, 32.80 feet nearly. 
1 hectometer " 100 " "328 " " 

1 kilometer " 1000 " / " 3280 « 

APPLICATION. 

1. Aii engine shaft is 5 meters long, what is its length in feet 
and inches? Ans. 16 ft. 4 J ins. nearly. 

_ . 39.37 X 5 1 _ ■ ., , 

Operation : -— == lb. 4 ft. nearly. 

2. An engine cylinder is 10.3 decimeters in diameter, how 
much is this in inches? Ans. 40-J- ins. nearly. 

Operation; 3.937 X 10.3 =40.55 ins. nearly. 



810 HANDBOOK ON ENGINEERING. 

3. A piston-rod is 8.7 centimeters in diameter, how much is 
this in inches? Ans. 3g ins. nearly. 

Operation : .3937 X 8.7 = 3.42 ins. nearly. 

4. A chimney is 5.1 decameters tall, how much is this in feet 
and inches? Ans. 167 ft. 3 ins. nearly. 

Operation : 32.80 X 5.1 = 167.28 ft. 

5. How many miles are there in 30.2 kilometers? 

Ans. 18 T 7 ^ miles nearly. 
Operation : There are 5280 ft. in a mile. 

™ 3280 X 30.2 iQ _ ... 

Then, =18.7 miles. 

5280 

6. A valve has 2 millimeters lead, how much is this in frac- 
tional parts of an inch? Ans. ¥ 5 ¥ in. nearly. 

Operation: .03937 X2 = .07874. 
And, .07874 X 64 = ^ f nearly. 

7. How many square feet in a circle whose diameter is one 
meter? Ans. 8£ nearly. 

n 39.37 X 39.37 X .7854 

Operation : — — = 8.45. 

144 

8. The cylinder clearance is 1.1 cubic decimeter, how many 
cubic inches in the clearance? Ans. 67 nearly. 

Operation: 3.937 X 3.937 X 3.937 X 1.1 = 67.12+ 



1 gramme equals 15.433 grains, or 1 ounce nearly. 
1 kilogramme equals 2.2047 pounds avoirdupois. 
I tonne equals 1.1024 tons of 2000 lbs. 

ALSO. 

1 litre equals 1.0566 quarts. 



HANDBOOK ON ENGINEERING. 811 



CONSEQUENTLY. 

1 U. S. gallon equai s 3.79 litres nearly. 
1 U. S. pint equals .4732 litres nearly. 

1. A main shaft weighs 800 kilogrammes, how much is this in 
avoirdupois pounds ? Ans. 1763| lbs. nearly. 

Operation : 2.2047 X 800 = 1763.76. 

2. An engine weighs 12 tonnes, how much is this in U. S. tons 
of 2000 lbs. each? Ans. 13} tons nearly. 

Operation: 1.1024 X 12 = 13.2288. 

3. A tank contains 9000 litres of water, how much is this in 
U. S. gallons? Ans. 2377.35 galls. 

1.0566 X 9000 
Operation: r Because 4 quarts equal 1 gallon. 



THERMOMETERS. 

In the U* S» the Fahrenheit scale is the one in most common 
use, although in our laboratories and for scientific purposes it is 
displaced by the Reaumer and Centigrade scales. Fahrenheit's 
scale marks the boiling point by 212 degrees, and the freezing 
point by 32 degrees above zero. 

The Reaumer scale marks the boiling point by 80 degrees, and 
the freezing point by zero. 

The Centigrade, or Celsius scale, marks the boiling point b}^ 
100 degrees, and the freezing point by zero. So that, reckoning 
from the freezing point of Fahrenheit, 180 degrees Fah. equal 
80 degrees Reaumer, and 100 degrees Centigrade. Bearing in 
mind that Fahrenheit's zero is 32 degrees below the freezing point, 
one scale may readily be converted into another. 

To convert degs. of Reaumer into those of Fah. 

Rule* — Multiply by 9, divide by 4, and add 32. 



812 HANDBOOK ON ENGINEERING. 

Example: #0 clegs. Reaumer equals how many (legs. Fall? 

Ans. 212. 
Operation: 80 X 9 = 720. 

720 
And, __ = 180. Then, 180 + 32 =212. 
4 

To convert the clegs, of Centigrade into those of Fahrenheit. 
Rule. — Multiply by 9, divide by 5, and add 32. 
Example : 100 degs. Centigrade equal how many degs. Fah. ? 

Ans. 212. 
Operation: 100 X 9 = 900. 

a i 900 
And, = 180. 

5 

Then, 180+ 32 = 212. 

So, also, 3 degs. Centigrade equal 37.2 degs. Fahrenheit. 

Thus: 3X9=27. And, =5.2. Then, 5.2 + 32 ==37.2. 

o 

ROPE TRANSMISSION. 

There are two systems of rope transmission, the English, 
or multiple-rope system, and the American or continuous wound 
rope system in which the necessary adhesion of rope to sheave is 
obtained by a tension carriage. I will treat of the American sys- 
tem only, as it is almost universally used in this country to the 
exclusion of the other. One of the most common mistakes is to 
lead the rope to the tension carriage from the tight or pulling 
side of the drive, and putting on an abnormal amount of tension 
weight in a vain endeavor to take out the slack. Under the enor- 
mous strain of such an arrangement the rope wears out very rap- 
idly, and more frequently parts at the splice. It is desirable in 
all cases of rope transmission to so arrange the drive that the 
slack side of the rope shall be on the upper part of the pulley 



HANDBOOK ON ENGINEERING. 



813 



thus increasing the arc of contact, as the two sides will then 
approach each other when in motion. The working strain in 
pounds on a rope should not exceed 200 times the square of the 
diameter of the rope. The speed of the rope should not exceed 
5500 feet per minute, and this speed gives the best results in 
H. P. The practical limit to the number of ropes for one sheave 
cannot be definitely named. The only limiting condition is the 
ability of the tension carriage to keep up the slack and when the 
number of ropes exceeds the capacity of one carriage, a second 
may be added and the drive made double. Diameters of sheaves 
should not be less than 40 diameters of the rope, and 50 to 60 
diameters are advisable, being justified by greater length of life 
of the rope. 

HORSE POWER TRANSniTTED BY ROPES. 

The following table gives the horse-power transmitted by a 
single manila rope when the arc of contact is not less than 165 
degrees, and the tension not greater than 200 times the square of 
the diameter of the rope. 



Velocity 






Diameter of Rope. 






of Rope in 
Feet per 

Minute. 
















'7s" 


8 / 4 " 


r 


U" 


H" 


1|" 


2" 


1000 .... 


1.24 


2.25 


3.57 


5.59 


8.02 


10.85 


14.20 


2000 


2.70 


3.84 


6.84 


10.68 


15.39 


20.93 


27.36 


2500 


3.30 


4.71 


• 8.38 


13.10 


18.86 


25.66 


33.54 


3000 .... 


3.83 


5.46 


9.80 


15.39 


21.87 


29.74 


38.88 


3500 


4.30 


0.23 


11.09 


17.33 


24.94 


34.03 


44.35 


4000 


4.74 


6.83 


12.15 


18.98 


27.33 


37.17 


48.59 


4500 


5.01 


7.24 


12.89 


20.15 


29.00 


39.45 


51.57 


5000 


5.20 


7.47 


13.29 


20.76 


29.89 


40.65 


53.15 


5500 


5.29 


7.60 


13.53 


21.14 


30.43 


41.39 


54.11 


6000 


5.08 


7.32 


13.10 


20.36 


29.32 


39.77 


52.12 


62)00 


4.74 


6.83 


12.13 


19.00 


27.34 


37.21 


48.63 


7000 


4.12 


5.93 


10.54 


16.47 


23.72 


32.26 


42.18 


7500 


3.25 


4.67 


8.32 


13.00 


18.73 


25.42 


33.23 



814 



HANDBOOK ON ENGINEERING. 



TO TEST THE PURITY OF ROPE. 

A simple test for the purity of manila or sisal rope is as fol- 
lows : — 

Take some of the loose fiber and roll it into balls and burn 
them completely to ashes, and, if the rope is pure manila, the ash 
will be a dull grayish black. If the rope be made from sisal the 
ash will be a whitish gray, and if the rope is made from a com- 
bination of manila and sisal the ash will be of a mixed color. 



WIRE ROPE DATA. 




HOISTING ROPE. 




PATENT 


FLATTENED STRAND. 




HEKCD- 


CRUCI- 


IRON. 


OQ 


LES. 


BLE. 




H 

w 
o 
g 

d 

S 


o 


°-2 


o 

o . 


S3 . 


O 

. 


S3 . 

22 




sa s - 




no 
7s '3 ^ ' 

* m ® 


8 fl 


b£.2o 

2-o 


Ch 


03 « 


IPH 




54 


oa^ 


i 


V.li 


13.5 


14* 


9 


10?, 


4 


g 


2<;i 


22.5 


i«i 


15 


IW 


6 


l 


35 


32 


24 


21 ! 


21 


9 


g 


45 


40.5 


30 


29 i 


26 


18 ; 


r.6? ; 


56 


39£ 


38 


34 


17 


H 


fi8 


67 


50 


47 : 


43 


21 1 


i* 


82 


84 


59* 


•56 j 


52 


28 




123 


124 


86 


81 i 


74 


40 


] l 


1 73 


168 


121 


109 | 


104 


54 


2* 


■>0;> 


211 


144 


140 


121) 


66 1 


2J 


257 


260 


18^ 


176 1 


152 


75 1 



19 


WIRE ROUND STRAND. 




HERCU- 
LES. 


CRUCI- 
| BLE. 


IRON. 


O 


S3 . 




S . 


g 


a . 





. 


HZ 


O . 


HZ 


O . 


O 03 


g 


£"3 


M .5 uf 




bC.£o 

a 




ta.So' 

S3 

3 .52" 


M 

5 


1-2 




fc.* 3 


.2- 


2£o 


cu 


CO <° 


Cm 


CQ " 


Cm 


CQ °° 


a 


16* 


12.5 


11 


8.8 


8 


4 


1 


22A 


20 


14 


13.6 


12 


6 


1 


30 


29 


18 


19.4 


16 


9 


J 


39 


36 


23 


26 


20 


13 




48* 


50 


30 


34 


26 


17 


1& 


57A 


60 


38 


42 


33 


21 


H 


71 


77 


46 


50 


40 


25 




103 


11,3 


66 


72 


57 


36 


if 


147 


157 


93 


96 


80 


48 


2 


172 


191 


111 


124 


92 


62 


21 


2 1 8 


238 


142 


156 


117 


74 



HANDBOOK ON ENGINEERING. 815 



ALTERNATING CURRENT MACHINERY. 

CHAPTER XXIX. 

THE PRINCIPLES OF ALTERNATING CURRENTS. 

The actions of alternating currents are not so easily under- 
stood as those of continuous currents and to most men not 
familiar with the subject they appear to be a mystery that can 
only be fathomed by those who are well versed in the higher 
branches of mathematics. As a matter of fact, when we once 
get on the right track, alternating current actions present no more 
difficulty to the man of fair mental ability, who is willing to work 
to learn, than the more simple continuous current actions. What 
makes alternating currents difficult to understand is, that in con- 
sequence of the ever-changing strength of %e current, inductive 
actions are developed that react upon the uirrent itself so that it 
becomes impossible to determine the magnitude of the current, 
the e.m.f. or the energy flowing in the circ lit by the simple rules 
used for continuous currents. As the strength of an alternating 
current is constantly changing the magnitude of the inductive 
actions is constantly changing, and this fact further increases 
the difficulty of the subject. 

In studying the principles of continuous currents we learn that 
when a conductor is moved across a magnetic field an e.m.f. is 
developed in it ; and thus we understand the operation of a gen- 
erator, as we know that when the armature revolves, it carries 
the conductors upon its surface through the magnetic flux that 
issued from the poles of the field. We further learn that inas- 



816 HANDBOOK ON ENGINEERING. 

much as the magnitude of the e.m.f. is increased by increasing 
the strength of the magnetic flux, or the number of conductors 
on the armature or the velocity of rotation, that one or all these 
factors must be increased to increase the voltage. Thus we come 
to consider that to induce a high e.m.f. we must have a strong 
magnetic field. Now one of the first things that the student of 
alternating currents finds out is that in an alternating current 
circuit, the strongest e.m.f. induced by the action of the current 
itself, comes at the very time when the magnetic field is the 
weakest, and this appears to him to completely upset all the 
principles of continuous currents ; but in reality it does not. 
To be able to get over this stumbling block successfully it is 
necessary to realize that the magnitude of the e.m.f. induced in 
a conductor that is moved through a magnetic field is not depend- 
ent upon the strength of the magnetic field, but upon the rate, 
or rapidity with which the conductor cuts the magnetic flux. 
Now it so happens that in a continuous current generator, the 
rapidity with which the conductors cut the magnetic flux increases 
with increase in the strength of the magnetic field, or the velocity 
of rotation, and thus it comes about that in this case, the increase 
in the induced e.m.f. appears to be due to increase in armature 
velocity or field strength when in reality it is due to increase in 
the rate at which the conductors cut through the magnetic flux. 
The magnetic flux developed by an alternating current alternates 
precisely as the current does, and, as will be clearly explained 
presently, this magnetic flux cuts through any conductors in its 
path, and the rate at which it cuts them is the greatest at the in- 
stant when the direction of the flux is changing, and this is the 
instant when the flux is nothing, so that the e.m.f. induced by 
the magnetic flux developed by an alternating current is the 
greatest at the very instant when the magnetic field has a zero 
strength. The foregoing facts can be made more clear by refer- 
ence to diagrams. 



HANDBOOK ON ENGINEERING. 



817 



Fig* i is a simple diagram that can be taken to represent a genera- 
tor, either of continuous or alternating currents. The dark circles 
A A, B B and G G represent the sides of three loops of wire 
which vi&y be regarded as wound upon the surface of an armature. 





JFUJl 



Fig. 1. 



The vertical lines represent a magnetic flux passing between the 
field poles Pand JV. If the armature upon which the three loops 
are mounted is rotated, e.m.fs., will be induced in each one of 
the loops, but the magnitude of these e.m.fs. will not be the 
same. If we take the instant when the loops are in the position 
shown, the e.m.f . in A A will be zero, while that in G G will be 
the highest and that in B B will be seven-tenths of that in G G. 
Now all these coils rotate at the same velocity being mounted upon 
the same armature, and all move through a magnetic field of the 
same strength, yet, in A A no e.m.f. is developed while in B B the 
e^m.f. is only seven-tenths of that developed in G G. The 
question is, why this difference? The answer is, that while loops 
A A move just as fast as G G they do not cut the magnetic flux 

52 



818 HANDBOOK ON ENGINEERING. 

because they are moving in a direction parallel with the lhes of 
force, the vertical lines, hence, the rate at which the magnetic 
flux is cut by them is zero, therefore the e.m.f . developed is zero. 
In B B the e.m.f. is seven-tenths of that developed ; n C (7, 
because the sides of this loop are moving in a direction that is 
not directly across the magnetic flux, but forms an angle of 45 
degrees with it, so that their actual velocity in a direction parallel 
with A A is seven-tenths of the velocity^of C G in this same 
direction. 

From the foregoing it will be seen that when we get down to 
a close examination of Fig. 1 we find that the magnitude of 
the e.m.f. developed in the several loops is directly proportional 
to the rate at which the sides of the loop cut through the 
magnetic flux. 

Let us now consider Fig. 2. In this diagram, circle A repre- 
sents a wire, seen end on, through which an alternating current is 
flowing. An alternating current is one that flows first in one 
direction, and then in the opposite direction, and continues 
changing the direction in which it flows at regular intervals of 
time. Now it is self-evident that if a current flows through a 
wire in alternate directions, it must stop flowing in one direction 
before it can flow in the opposite direction, that is at the instant 
when the direction of flow is changing, there can be no current. 
Such being the case, when the current begins to flow in either 
direction, it must increase in strength gradually up to a certain 
point, and then begin to decrease, so as to reduce to nothing at 
the instant when the direction of flow changes. As is explained, 
in the section on continuous currents, when a current of elec- 
tricity flows through a wire, a magnetic flux is developed around 
the wire and this can be represented by lines of force drawn in 
the form of circles, as in Fig. 2. If there is no current flowing 
through the wire there is no magnetic flux, therefore, if we 
consider the instant when a current begins to flow, w r e can imagine 



HANDBOOK ON ENGINEERING. 819 

that at this instant the magnetic flux begins to expand outward 
from the wire, and since the circular lines are drawn to represent 
this flux we can assume that these expand outward, like the rip- 
ples on tlie surface of a pond when a pebble is thrown into the 
water. So long as the current flowing through the wire increases 
in strength, just so long will the magnetic circles of force expand, 
but when the current reaches its greatest strength the circular 
lines of force will become stationary, and will remain so if the 
current remains at its maximum strength ; but if the current 
begins to reduce in strength as soon as it reaches its maximum, 
then the circular lines of force will begin to contract immediately 
after they stop expanding, just as a swing will begin to move 
backward the instant it stops swinging forward. 

If the circles B and C in Fig. 2 represent two wires parallel 
with A, it is evident that the magnetic circles of force when they 
move outward from A will cut through B and C in one direction, 
and when they contract back upon A they will cut through these 
two wires in the opposite direction. When these circular lines 
of force cut through the wires B G they will induce e.m.fs. in the 
latter, and if these e.m.fs. are positive when the lines of force ex- 
pand, they will be negative when the lines contract. When the 
current reaches its maximum strength and the circular lines of 
force become stationary for an instant, they will not cut the wires 
B and C and at this instant there will be no e.m.f. induced in 
these wires. Now the circular lines of force become stationary 
at the very instant when the current flowing through the wire 
reaches its greatest strength and is on the point of reducing, so 
that at this instant the e.m.f. induced in the wires B and C is zero. 

The highest e.m.f. induced in B and occurs at the instant 
when the current flowing through A is changing its direction, or, in 
other words, at the instant when there is no current. Just 
before the current reduces to zero, the circular lines of force 
are contracting upon wire A, and the instant after the cur- 



820 HANDBOOK ON ENGINEERING. 

rent reduces to zero and changes its direction, these lines 
of force will be expanding so that in the first case the lines 
of force will sweep over wires B and O in a direction toward 
A, and in the second case they will sweep over these wires in a 
direction away from A. From this fact it might be inferred that 
the e.m.f. induced in the two cases would be in opposite direc- 
tions, but this is not so, owing to the fact that the lines of force 
change in direction when the current changes, so that if while 
contracting they are directed clockwise, as soon as they begin to 
expand they will be directed counter clockwise. As a result of 
this change in the direction of the lines of force when they change 
from contracting to expanding, the e.m.f s. induced in B and G 
are in the same direction before the lines stop contracting and 
after they begin to expand. The circular lines of force stop con- 
tracting and begin to expand at the same instant, so that the 
inductive action developed by the contracting lines is followed up 
without a break by the expanding lines. In alternating currents 
such as are actually used in practice, the rate at which the 
strength of the current changes is the greatest when it is just 
beginning to grow, and when it is reduced almost to zero, and on 
this account the highest e.m.f. induced in wires B and G occurs 
at the instant when the direction of the current is changing, that 
is, when the current is zero. Alternating currents can be de- 
veloped in which the rate of change in the current is not the 
greatest just when they begin to grow and when they are reduced 
nearly to zero and with such currents the highest e.m.f. induced 
in wires B and G would not come at the instant when the current 
is zero, but would come at the instants when the change in the 
current is the most rapid. 

In every kind of alternating current, however, the instant when 
the e.m.f. induced in B and G is zero is the instant when the 
current reaches the maximum value, and begins to decrease, 
for this is the only instant when the circular lines of force are 



HANDBOOK ON ENGINEERING. 



821 



immovable ; it being the instant when they are about to change 
from expanding to contracting, while still flowing in the same 
direction. When the current becomes zero, the lines of force 
change from contracting to expanding but at this instant they 
also change their direction so that the new expanding circular 
lines of force take up the work if inducing an e.m.f. in the wires 
B and G at the very point where the contracting lines leave off. 

The circular lines of force developed by the current flowing 
in A cut through this wire as well as through B and (7, hence, 
they induce an e.m.f. in A; that is an alternating current induces 
an e.m.f. in its own circuit as well as in adjoining circuits. The 
action upon adjoining wires is called mutual induction, and that 
upon its own wire is called self-induction. These e.m.fs. act in 
a direction opposite to that of the current that induces them. 

The relations between alternating currents and e.m.fs. can be 
shown by means of diagrams, the simplest of which are con- 




FigS 



structed in the manner shown in Fig. 3. In diagrams of this 
type the line I 7 represents time, thus if a point is assumed to 
move from in the direction of T at a uniform velocity of say 
one foot per second, then a length of one inch will represent an 
interval of time of one-twelfth of a second. Distances measured 
in the vertical direction, along S represent the magnitude of 



822 HANDBOOK ON ENGINEERING. 

the current or e.m.f. Positive currents and e.m.f. are indicated 
above the time line T and negative currents and e.m.fs. below 
this line. Thus the wave line AAA can represent an alternating 
current or e.m.f. or an alternating magnetic flux. This curve it 
will be seen is above T from Otob, and below T from b 
to d, being again above from d to T. The two sections of the 
curve from to d constitute one cycle, or two alternations. The 
portions between the lines a, a b, b c, c d are called quarter 
cycles or quarter periods. The time from to d is called one 
period, and if this is equal to one-tenth of the distance that 
represents one second, then there are ten periods to one second. 
This fact is indicated by saying that the periodicity of the current 
is ten, or that its frequency is ten. The frequency of alternating 
currents in common use ranges between 20 and 130. 

The curve A A in Fig. 3 represents a current or e.m.f. that 
increases or decreases at a certain rate, but for a current varying 
at some other rate it would be necessary to use a curve of differ- 
ent shape to correctly represent it. Thus if the current does not 
increase so fast when rising from the zero value, but increases 
faster when nearing its maximum value we will require a modifica- 
tion of the curve such as is indicated by _B, in which the slope is 
more gradual on the start, and near the middle becomes more 
steep. If on the other hand the current increases more rapidly 
on the start, and less rapidly as it approaches the maximum value, 
we will have to use a curve something like C which is steeper at 
the ends and flatter at the middle. 

The. actual form of curve required to correctly represent an 
alternating current depends upon the rate at which the current 
varies, and this rate depends upon the construction of the machine 
in which it is generated. For the purpose of simplifying calcula- 
tions it is necessary to assume that the rate of variation of a cur- 
rent is such that it can be represented in a diagram such as Fig. 
3 by some form of curve that can be drawn in accordance with 



HANDBOOK ON ENGINEERING. 



823 



some fixed rule. The curve A A is of circular form, but there 
are few alternating current generators that develop currents that 
such a curve can properly represent. 

If a current alternates in equal intervals of time, and the rate 
of variation is the same when it is flowing negatively as when it is 
flowing positively, then it can be represented by a curve that is 
of symmetrical construction, such as A A in which the intervals of 
time 5, b d are equal and the curves above the line T are of 
the same shape as those below it. Such a current is called a 
symmetrical periodic current, and it is the only kind with which we 
have to do in practice. It can be readily understood, however, 
that the current can be far from regular, that is, the time during 
which it flows positively can be more or less than the time during 
which it flows negatf \y, and the rate of variation in the two 



^ 


a 


^ >s^ 







\b/ 


b 


K, 



s 



o 



Fig4 

instances can be different. The curves in Figs. 4 and 5 illustrate 
currents of this kind. In Fig. 4 the positive impulses of the cur- 
rent are longer than the negative, as is shown by the greater 
length of lines a, b c as compared with a b. It will also be 
seen that the rate of variation is different as is indicated by the 
difference in the form of the portions A A and B B of the 
curve. In Fig. 5 the irregularity is still greater, as all the time 
intervals a, a 6, b c, c cl, are different, as are also the portions 
A B C D E of the curve. 



824 



HANDBOOK ON ENGINEERING. 



The alternating currents developed by alternating current 
generators have such a rate of variation that they can be repre- 
sented in diagrams by means of what is known as a sine curve. 




Fig.5 



This curve is not a perfectly true representation of practical 
alternating currents, but it comes so near to it that calculations 
based upon the assumption that the sine curve represents the actual 





g s 






-■ 


a a 


Z i \ 

/I iH 




1- 

_e 


6 


- 


t 




d 












T 


5^_ 


W- 

\ 1 X 

- 


* 


- 




-- 


- 




\ 


\ 


V 


J 


~i 


/ 





£ig.6 

variation, do not depart from the truth by more than two or three 
per cent, and in some cases less than that. As the sine curve is 
commonly used to represent alternating currents we will show 



HANDBOOK ON ENGINEERING. 825 

how it is constructed by the aid of Fig. 6. In this diagram dia- 
metrical lines a b c are drawn on the circle B, dividing it into 
any desired number of equal parts. A distance T on the hor- 
izontal line is divided into an equisl number of equal parts and 
perpendicular lines a a are drawn at these divisions. From the 
points where the liness a b c cut the circle lines are drawn parallel 
with T as shown at e / g and the points where these cut the 
corresponding perpendicular lines a a form points of the sine 
curve A A. The distance T can be made anything desired 
without affecting the character of the curve, the only difference 
being that if it is short the curve will be more pointed than if it 
is long. 

One reason why it is assumed that alternating currents vary 
in accordance with a sine curve is that if the variation is at this 
rate the e.m.f . induced by the magnetic flux developed by the 
current will also vary in accordance with the sine curve, so that 
the current, the magnetization and the induced e.m.f. can be rep- 
resented by sine curves, and thus the process of calculating the 
effect of the induced e.m.f. upon the strength of the current can 
be greatly simplified. 

By looking at Fig. 1 it can be seen at once that if the 
loop A A is revolved at a uniform velocity, and the 
magnetic field between the poles P and N is of uniform 
strength at every point, the e.m.f. induced in A A will 
vary in strict accordance with the variations of the sine 
curve A A of Fig. 6, for in the position A A the e.m.f. will be 
zero, and in position C C it will be the maximum, while in any in- 
termediate position such as B B it will be equal to the actual velocity 
of the sides of the loop measured in the direction parallel with 
A A , and this velocity is equal to the distance of the side of the 
loop from the horizontal line A A. Now the height of the sine 
curve A Am Fig. 6 at any point is also equal to the distance from 
the end of the corresponding line in circle B from the horizontal 



826 



HANDBOOK ON ENGINEERING. 



line, that is, the distrance e e' from the horizontal line to the curve 
is the same as the distance e e on the circle. 

The complete sine curve from to Tis traced by following the 
rotation of the radius of the circle through one complete revolu- 
tion. On that account this distance T is taken to represent one 
revolution, and is divided into 360 degrees, the same as the 
circle. Half the distance, or d, is equal to 180 degrees, and 
one-quarter the distance is 90. The vertical lines a a in Fig. 6 
are 30 degrees apart. 

The way in which sine curves are used to represent alternat- 
ing currents and e.m.fs. is shown in Fig. 7. In this diagram, 



(h a 




let the curve A represent an alternating current flowing through a 
wire. As is fully explained in the foregoing, this current will 
develop an alternating magnetic flux, and this flux will increase 
and decrease as the current increases and decreases, that is, it 
will keep in time with the current, or in step with it, as it is com- 
monly expressed. Such being the case, the curve A can be used 
to represent the magnetic flux as well as the current, providing 
we assume a proper scale for both. Looking at the half circle to 
the left of the figure, it will be seen that curve A is described by 



HANDBOOK ON ENGINEERING. 827 

a radius rotating around the middle circle. Remembering what 
was said in connection with Fig. 2 as to the time relation between the 
magnetic flux and the e.m.f . induced thereby, we will realize that 
at the instant when the flux is zero, the induced e.m.f. must 
be at the maximum value, and it will act in opposition to the 
e.m.f. that drives the current through the wire, hence, in the 
diagram, it will have to be drawn below line T. Let the maxi- 
mum value of this induced e.m.f. be equal to c, then for all 
other values it will be correctly represented by the sine curve B, 
which is traced by the rotation of the radius of the inner circle. 

At the instant of time 0, the magnetic flax is zero, hence the 
radius of the middle circle from which curved, is traced must be 
in the direction of line T. At this same instant the induced 
e.m.f, is at the maximum value hence the radius that traces 
curve B must be in the vertical position parallel with c. From 
this we see that in relation to time the curves A and B that repre- 
sent the magnetic flux and the induced e.m.f. are one-quarter of 
a cycle apart, that is the induced e.m.f. is 90 degrees behind the 
magnetization, and also 90 degrees behind the current that flows 
through the wire. 

No kind of electric current, whether continuous or alternating, 
can flow through a circuit unless there is an e.m.f. to drive it, 
and this e.m.f. must be sufficient to impel the current against 
all resistances of any kind that it may encounter. The e.m.f. 
that impels a current through an alternating current circuit is 
called the impressed e.m.f. In Fig. 7 it is evident that the 
impressed e.m.f. must be sufficient not only to overcome the 
actual resistance that opposes the flow of the current represented 
by curve A, but also sufficient to overcome the opposing action of 
the induced e.m.f. represented by curve B. Now the e.m.f. 
required to overcome the resistance that opposed the flow of the 
current can be represented by the curve A, in precisely the same 



828 HANDBOOK ON ENGINEERING. 

way as this curve represents the magnetization ; hence, the curve 
C which represents the impressed e.m.f. must at every point be 
equal, in height, from the line T, to the sum of the heights of the 
curves A and B, when these two curves are on opposite sides 
of T, or to their difference when they are on the same side. At 
the instant it is clear that as the current is zero, the impressed 
e.m.f. must be of the value c' to balance the induced e.m.f. 
B for if it were not, there would be a current flowing negatively 
under the influence of e.m.f. B. At any instant between C and 
cl, the impressed e.m.f. C must be equal to the sum^Landl?, that 
is, the distance from C to the time line T must be equal to the 
distance between the curves ^i B measured on the same vertical line. 
At the instant d the induced e.m.f. is zero, hence the impressed 
e.m.f. is equal to the distance of curve A above line T. For 
any interval of time between d and e, the impressed and the in- 
duced e.m.fs. are acting together, so that the first named, that is, 
curve 0, need only be equal to the difference between A and B. 

By studying the diagram Fig. 7 it will be seen that the curve 
O, which represents the impressed e.m.f., is described by the 
rotation of the radius of the outer circle at D, and in order that 
this e.m.f. may have the value of c' at the instant 0, it is nec- 
essary for the describing radius at this instant to be in the posi- 
tion b. From this it will be seen that the impressed e.m.f. is not 
in time with the current but in advance of it by a time interval 
that is equal to the angle formed by the radius b with the line 
T. 

If two alternating currents, e.m.f. or magnetic fluxes are 
in time with each other they are said to be in phase, but if they 
are not in time they are out of phase. In Fig. 7 the current, the 
impressed e.m.f. and the induced e.m.f. are out of phase with each 
other. The impressed e.m.f. leads the current, and the latter 
leads the induced e.m.f. This relation is also expressed by say- 



HANDBOOK OX ENGINEERING. 



829 



ing that the current lags behind the im- 
pressed e.m.f. and the induced e.m.f. 
lags behind the current. The current 
and the impressed e.m.f. can never be 
out of phase by an angle as great as 90 
degrees, but the phase difference can be 
any angle less than this. The induced 
e.m.f. is always 90 degrees out of phase 
with the current. The induced e.m.f. 
in the circuit in which the current flows 
is called the self-induction. 

The relations between the impressed 
e.m.f., the current and the self-induc- 
tion both in magnitude and phase are 
clearly shown in Fig. 8, which is simply 
an enlarged view of the left side of 
Fig. 7. The radius A of the outer 
circle is the impressed e.m.f. The 
radius B of the middle circle is the cur- 
-=» ,c5 rent, and the radius G of the inner 

circle is the self-induction. The magnitude of any one of these 
three quantities at any instant of time • is equal to the distance 
from the end of the line to the horizontal line. The radius B 
which represents the current is on the horizontal line, hence the 
current at the instant represented by the diagram is zero. The 
self-induction G has a value at this instant equal to the length of 
the line, that is, it is at the maximum value, and as it is below 
the horizontal line it is negative. The impressed e.m.f. A, has 
the value of a a, and being above the horizontal line, it is positive. 
The phase relation and also the magnitude of these quantities is 
also shown in Fig. 9, which is constructed from Fig. 8 by remov- 
ing the self-induction to the position of line a a. From Fig. 9 it 




830 



HANDBOOK ON ENGINEERING. 



can be seen that if we know two 
of the quantities we can always 
determine the other one by sim- 
ply constructing a right angle 
triangle, 

The self-induction acts to 
oppose the flow of current, 
hence it is equivalent to the 
addition to a certain amount of 
resistance to the circuit, but as 
can be seen from the diagrams 
it cannot be added directly, 
after the fashion in which 
numbers are added. To add it 
properly it must be placed at 
right angles to the resistance. 
If the self-induction is divided 
by the strength of the current, 
we get a quantity that can be 
compared with the resistance, 
and this quantity is called the 
reactance and is measured in ohms precisely as the resistance is. 
The flow of current in a continuous current circuit is opposed 
by the resistance only, but in an alternating current circuit it is 
opposed by the resistance and the reactance and the combined 
effect of these two is called the impedance of the circuit. 

The relation between resistance, reactance and impedance is 
the same as that between impressed e.m.f., current and self- 
induction, and is shown in Fig. 10. 

The reactance multiplied by the current gives the self-induction. 
The impedance multiplied by the current gives the impressed 
e.m.f. 




RESISTANCE. 

Fig,10 



HANDBOOK ON ENGINEERING. 



831 



The resistance multiplied by the current gives the e.m.f. in 
phase with the current, which is also called the active e.m.f. 

A sine curve diagram, such as is shown in Fig. 
7, serves very well to enable the learner to under- 
stand the relation between the current and e.m.fs. but 
when this relation has been fully mastered, what is known 
as a clock dial diagram becomes more convenient, specially 
if we desire to represent several currents and their e.m.fs. Fig. 8 
is virtually one-half of a clock dial diagram. A regular clock 
dial diagram to represent a single alternating current is shown 
in Figs. 11. 12, 13. The radius A represents the current, and is 




Fig.ll 



Fig.12 



Fig J 3 



supposed to rotate at a velocity equal to the frequency of the 
current. The strength of the current for any instant of time is 
obtained by measuring the distance from the horizontal line S S 
to the end of the radius at that particular instant as indicated by 
line a a in Fig. 12. If A is above the line S S the current is 
'positive, and if it is below S S the current is negative. At the 
instant when A is in the vertical position, as in Fig. 13, the 
current is at its maximum value, and when A is horizontal as in 
Fig. 11 the current is zero. If we desire to find the relation 
between the current and impressed e.m.f. or the self-induction, 
we draw radial lines of the proper length to represent these 
e.m.fs. and in the proper angular position with reference to the 
current and then assume them to be locked together when they 



832 



HANDBOOK ON ENGINEERING. 



are rotating so that the distances from the ends of each one to 
the line S S at any instant gives the values of the quantities at 
this instant. 

Diagrams of this type are specially valuable for the represen- 
tation of polyphase currents. Currents of this type are commonly 
spoken of as a two-phase current, or a three-phase current, or a 
polyphase current. Now there are no multiplephase currents. 
What is improperly called a two-phase current is a combination 
or two simple alternating currents so timed that they are out 
of phase with each other by one quarter of a period, or revolu- 
tion. This constitutes a system of two-phase currents. Three 
simple alternating currents so timed as to be out of phase with 
each other by one-third of a period, constitute a system of three 
phase currents. In the first case we have two currents, and in 
the second we have three currents. These currents in either 
system are connected so as to act together in the same system 
of circuits. If the phase relations are not such as given above f 
they cannot constitute true, two or three-phase systems. 




Fig.14 



Fig.m 



The phase relations for the two-phase system are shown in Fig. 
14 and for the three-phase system in Fig. 17. The two currents 
A B in Fig. 14 are at right angles with each other, and the three 
currents in Fig. 17 are 120 degrees apart, or one-third of a 
period, or cycle. To obtain the values of the two currents in 



HANDBOOK ON ENGINEERING. 



833 



Fig. 14 at any particular instant, they are rotated together as is 
indicated in Figs. 15 and 16. The values will be equal to the lines 
a a and b b. In the same way the values of the three currents in 
a three-phase system are obtained for any instant as is illustrated 
in Figs. 18 and 19. 

For the transmission of the currents of a two-phase system, 
three or four wires can be used. In the three-phase system, if 
the three currents are equal, three wires are sufficient, but if these 
currents are not equal a fourth wire is required to carry the surplus 




Fig.17 



Fig.18 



current as it may be called. When the three currents of a three- 
phase system are equal it is called a balance system, but if they 
are not equal the system is unbalanced. In Figs. 17 to 19 the 
three currents are drawn of equal length and it will be found that 
in every position in which the lines can be placed the sum of the 
two currents on one side of line S S will be just equal to the cur- 
rent on the other side, so that if the current is flowing away from 
the generator through one wire, it will divide up and return 
through the other two, and provide for each wire just the amount 
of current required. Thus in Fig. 17 the current flowing in A is 
zero, and the positive current in B is equal to the negative current 
in 0. In Fig. 18 the two positive currents a a and b b in lines 
A B, are just equal to the one negative current in C, and this 
is also the case in Fig. 19. 



834 HANDBOOK ON ENGINEERING. 

Unbalanced three-phase currents are seldom used, but when 
they are, a fourth wire is run from the point where the three 
circuits ABC are joined, to a corresponding point at the genera- 
tor end of the circuit, and then any excess or deficiency of current 
that is not provided for by the three regular circuit wires is taken 
through the fourth wire. The point where the three wires join, 
at the center of the circle, is called the neutral point, and the 
wire connecting then is the neutral wire. Two and three-phase 
systems are used almost exclusively for the transmission of power 
to great distances, and for this work only three wires are used. 

Polyphase systems can be formed of any number of currents, 
but they would be of no practical value, owing to increased com- 
plications, and on that account are not used. In addition to the 
one, two and three-phase systems, explained in the foregoing, the 
only system that has been used to any extent is the ' ' monocyclic, ' ' 
which was introduced by the General Electric Company. This 
system may be described as a sort of cross between the single 
phase and the polyphase systems. It consists of two currents, 
90 degrees out of phase, just as in a two phase system, but in- 
stead of the two currents being equal, one of them is four times 
the strength of the other. The armature coils of the generators 
that furnish these currents are so connected with each othe«r 
that the two currents, as fed into the line wires, constitute an 
unbalanced three-phase system. This arrangement of the generator 
coils will be found more fully explained in the section on " Alter- 
nating Current Generator," and the object of the " monocyclic " 
system will be found explained in the section on " Transmission 
Systems." 

Induetive Action in Alternating Current Circuits. — In Fig. 20 
let G represent an alternating current generator that impels an 
alternating current through the circuit A A. This current as 
already explained will develop a magnetic flux around the wire 
such as is indicated at C D. This flux will develop a self-indue- 



HANDBOOK ON ENGINEERING. 835 

tive e.m.f . in the circuit and thus retard the current, so that the 
actual amount of current flowing will be less than it would be in 
a continuous current circuit acted upon by an impressed e.m.f. of 
the same magnitude. As will be noticed, the direction of the flux 
at C and D is such that they oppose each other, that is the lines 
C and D flow through the space between the two sides of the loop 
A A in opposite directions, and on that account the lines C can 
only extend to the ^center of the space, while lines D will occupy 
the upper half. This being the case it is evident that if the cir- 
cuit wires are brought closer together as indicated by the lines 
B B, the magnitude of the magnetic flux that will surround each 
wire will be correspondingly reduced as is indicated by the lines a a. 
The self-inductive e.m.f. developed in the circuit will be propor- 
tional to the magnitude of the flux that surrounds the wire, hence 
the nearer the two sides are brought to each other the less the 
self-induction, and if the two wires could be placed side by side 
the inductive effect would be practically nothing. From this it 



-Hi 




ViifiV n 



a 




Fi4.2Q 

will be seen that if an alternating current is transmitted to a dis- 
tance the nearer the line wires to each other the smaller the self- 
induction developed in them. 

In an alternating current circuit the self-induction developed in 
every portion is not the same, and the total effect is equal to the 
sum of the several effects. For example in Fig. 21 let A A A 
represent a circuit that is fed by a generator at G. The self- 



836 



HANDBOOK ON ENGINEERING. 



induction on the line A will be small, specially if the wires 
are placed near each other. If a number of incandes- 
cent lamps are connected at C the self-induction of these 
will be practically nothing. If at B we place some kind of 
device that is provided with wire in the form of coils, then at this 
point a large self-induction will be developed, for then the 
magnetic flux from each turn Of wire in the coil will be able to cut 



A 



A 



A 






a 



Fi*.M ^ Av 



through many other turns, and thus greatly increase the inductive 
action. To determine the total amount of inductive action in 
this circuit, so as to ascertain the amount of current that 
will flow through it, we will have to find the total impedance 
of the circuit, and this we do by finding the impedance of each 
part and then adding these impedances, but all this operation is 
carried out not in the way in which we add figures, but in the 
manner shown in Fig. 10. The diagram Fig. 22 illustrates the 
operation. By actual measurement we can find the resistance of 
the line A in ohms and we can mark it down on the diagram as 
o a. By calculation, we find the reactance of line A and mark it 
down as a a', thus we obtain the impedance of o a' of the line. 
Next, we find the resistance of the lamps C which we mark down 
at a' 5, and from b draw b b' equal to the reactance of the lamps, 
thus obtaining the impedance a' &', of the lamps. We now draw 
b' c equal to the resistance of B and c c' equal to the reactance of 



HANDBOOK ON ENGINEERING. 



837 



B and thereby obtain the impedance b' c' of B. We now join o 









^^7 
















^**"^ ** 








**^ • 








• 




c^^ 




• 






b'y 


^^^J£== 


-• 


—f-- 


......... 


^< :r< -~ " ! 




"% 


A 


a 









FlgS2 

with c' and obtain the line G which is the total impedance of the 
circuit, and line B, which is the total reactance, while line A is 
the total resistance. A glance at the diagram will show that the 
total impedance G is less than the sum o a' a' b' and b' c' if these 
were added in the ordinary way, so that the total impedance of a 
circuit can be less than the direct sum of the impedances of its 
several parts. 




Fig.23 

The angle of lag between the current and impressed e.m.f. 
in an alternating circuit plays a very important part in determin- 
ing the actual amount of energy that is transmitted. In a 
continuous current circuit the energy is always equal to the 



38 



HANDBOOK ON ENGINEERING. 



product of the volts by the amperes but in an alternating circuit 
it may be equal to this product and it may not be as much 
as one per cent of this product. What proportion of the product 
of the volts by the amperes will represent the actual energy trans- 
mitted will depend upon the angle of lag between the current 
and the impressed e.m.f., the greater this angle the less the en- 
ergy. The way in which the angle of lag affects the amount of 
energy flowing in the circuit can be made clear by means of Figs. 
23 to 25. In these figures, curve A represents the impressed 
e.m.f. and curve B is the current, while the shaded curves repre- 
sent the energy. In Fig. 23 the impressed e.m.f. and the current 




are shown in phase with each other, and as a result the curves G 
which represent the energy are drawn above line T, thus show- 
ing that all the energy is positive, and it is equal to the direct 
product of the volts by the amperes. In Fig. 24 the current and 
impressed e.m.f. are drawn out of phase 90 degrees. Starting 
from 0, the e.m.f. is positive while the current is negative, curve 
B being below line T. This means that the current and e.m.f. 
act against each other hence the energy represented is negative. 
After the first quarter of a period, the current becomes positive 



HANDBOOK ON ENGINEERING. 



839 



and then the energy is positive. Thus for the first half period we 
have two energy curves, D negative, and C positive, both of these 
are equal and, therefore, just offset each other, so that the net 
energy flowing in the circuit during this time is zero. As will be 
seen, during the following half periods, the same operation is re- 
peated, so that the actual result is that energy is put into the circuit 
during one quarter period, and during the next quarter it is taken 




Iig.%5 



out, and the actual energy flowing through the circuit is nothing. 
The action is the same as when a swing is set in motion, during 
the first half of each swing energy is accumulated by the descent 
of the weight, but during the next half it is all absorbed in lifting 
the same weight, and unless we supply from outside enough en- 
ergy to overcome the friction the swing will soon come to a 
standstill. In an alternating current circuit, if the impressed 
e.m.f. and the current were out of phase 90 degrees no energy 
would be introduced into the circuit, hence, no current at all 
could flow, but if the angle is a trifle less than 90, say 89, a suf- 
ficient amount of energy can be put into the circuit to overcome 
the resistance loss, and then a strong current will sway back and 
forth that is not capable of doing any work. A current of this 



840 HANDBOOK ON ENGINEERING. 

kind is called a wattless current as it carries no energy. The rea- 
son why it carries no energy is that the self-induction very nearly 
balances the impressed e.m.f . so that the effective e.m.f . is very 
small, in fact it is just enough to force the current against the 
resistance of the circuit. 

In Fig* 25 the current and imprissed e.m.f. are shown out of 
phase by an angle of 45 degrees, and as will be seen the shaded 
curves G which represent positive energy, are much larger than 
those below line T, which represent negative energy. The 
difference between these two is the actual energy flowing in the 
circuit. It can be clearly seen that the smaller the angle of lag 
between the current and impressed e.m.f. the larger the shaded 
curves above line T and the smaller those below the line ; 
hence, the greater the energy flowing in the circuit. 

By the use of condensers, the effect of self-induction can" be 
counteracted, and in that way the lag of the current can be re- 
duced and thus the energy in the circuit can be increased. A 
condenser is a device that is so constructed as to be able to re- 
ceive a very large electriostatic charge. To explain the nature 
of electrostatic charges so that they may be understood we may 
say that bodies arranged so as to hold a charge will carry this 
charge upon their surface. Thus we can picture to the mind's 
eye the charge as flowing over the surface until it completely 
covers it. When a condenser is used in an alternating current 
circuit, it is charged and discharged each time the current 
alternates, and the time relation of the charging and discharging 
currents is such as to be directly opposite to the current that would 
flow under the effect of the self-induction, or, to put it in another 
way, the e.m.f of the condenser current is 180 degrees out of 
phase with the self-induction. Now, by properly proportioning 
the condenser it can be made to just balance the self-induction, 
and then we get the relations illustrated in Fig. 26 in which curve Z? 
represents the self-induction, curve C the condenser e.m.f. which 



HANDBOOK ON ENGINEERING. 



841 



is directly opposite and of equal magnitude. Curve A represents 
the impressed e.m.f. as well as the current, both being in phase 
with each other. 

The general principle of construction of a condenser is illus- 
trated in Fig. 27, in which the plates A B represent the condenser, 




Fig. 26 

and G the generator that provides the current, the connecting 
wires being S S. A device of this kind, if placed in a continuous 




Fig. 2 7 



current circuit, will simply prevent the flow of current ; but when 
connected in an alternating current circuit, if of the proper pro- 
portions, will act as if it did not break the circuit. This is because 



842 HANDBOOK ON ENGINEERING. 

the large surfaces on the plates A B act as reservoirs and accumu- 
late all the current that flows into them during the short time each 
impulse lasts. When the current reverses, the charge in the con- 
denser runs out together with the generator current. We 
can thus consider that if a positive impulse of the current fills 
plate A and empties plate 5, a negative impulse will reverse the 
operation. 

Mutual induction* — In connection with Fig. 2 it was shown 
that when an alternating current flows through a wire, the alter- 




Fig.28 

nating magnetic flux that surrounds the wire, if it cuts through 
any other wires running parallel with it will induce e.m.fs. in 
them. The direction and phase of these e.m.fs. will be the same 
as that of the self-induction in the wire carrying the current. If 
we have two wires running parallel with each other and alternat- 
ing currents flow through, then the action of wire No. 1 upon 
wire No. 2 will be the same as that of No. 2 upon No. 1. This 
action is called mutual induction, and it is made use of in the 



HANDBOOK ON ENGINEERING. 843 

construction of an apparatus used for transforming alternating 
currents which is commonly called a transformer. 

By the aid of Fig. 28 the principles of mutual induction can be 
made quite clear. In this diagram suppose that the circle A rep- 
resents one wire through which an alternating current is flowing, 
and circle B represents another wire carrying an alternating cur- 
rent. If these two wires are some distance apart, it is clear that 
a considerable portion of the magnetic flux of A will not cut 
through 5, and in like manner that a considerable portion of 
the flux of B will not cut though A, as is indicated by 




FigJSd 

the dotted circles at a a a. In any case, however, some 
of the flux of one wire will cut through the other. From 
this it follows that the effect of the current in each wire 
upon the other wire will be less than that upon itself, 
but the closer the wires are to each other the nearer equal 
the effects will be. When it is desired to avoid the effects of 
mutual induction as far as possible the wires must be separated 
to the greatest distance, and when we desire to make the mutual 
inductive effect the greatest, we must bring the wires as close 



844 HANDBOOK ON ENGINEERING. 

together as possible. The inductive effect of wires upon each 
other in some cases produces very objectionable results, for 
example when telephone wires are run side by side for any 
distance the inductive action of one wire upon the other serves 
to render the conversation indistinct. Why this is so it can be 
appreciated at once from an inspection of Fig. 29, which shows 
a pole carrying four wires. Telephone currents are not alter- 
nating but they pulsate and thus produce the same effect as if 
they were alternating. In Fig. 29 the circles drawn around 
each one of the wires as will be seen cut through all the other 
wires. If the two upper wires belong to one circuit and the two 
lower ones to another, then if one set of wires are crossed at every 
three or four poles so that the wire running on the right side 
for a certain distance will then be changed over to the left side, 
the inductive actions will be counteracted to a very great extent 
and this method is followed in stringing telephone wires. It is 
also used in regular alternating current circuits when interference 
between different circuits is to be avoided. 

With regards to the two wires belonging to the same 
circuit, it is advantageous to string them as close together as 
possible, for in this case, the effect of mutual induction is to 
neutralize the effect of self-induction. Referring to Fig. 20 it 
can be seen at once that if the magnetic flux at C develops a self- 
induction in lower A toward the right, it will develop an induc- 
tion in upper A also towards the right, but with reference to the 
wire itself this induction will be just opposite to that in the lower 
side so that the two will counteract each other. Thus to reduce 
the reactance of the line, the two sides of the circuit must be 
placed as near together as is practicable. 

Transformers^ — A transformer is an apparatus in which the 
principle of mutual induction is utilized for the purpose of gener- 
ating a second current by the inductive action of a primary 
current. Referring to Fig. 28 it can be seen that if wire B is 



HANDBOOK ON ENGINE EKING. 



845 



closed upon itself the e.m.f. induced in it by the magnetic flux 
issuing from A will cause a current to flow and then this current, 
which is brought into existence by the inductive action of the 
current in A, will in turn develop a magnetic flux that will react 
upon wire A in precisely the same manner as if the current were 
not induced in B, but it came from an independent source. In a 
transformer, the wire is wound in the form of compact coils, and 
one of these coils, which is called the primary, is connected with 
an alternating current circuit. The current flowing through this 
coil induces a current in the other coil which is called the second- 
ary. The general construction of a transformer can be under- 




Fig.80 



stood from Fig. DO. An iron core C is provided upon which are 
wound two coils marked A and B. The coil A which is the prim- 
ary, is connected with an alternating current circuit, and thus the 
iron coreO is strongly magnetized. The presence of the iron core 
C serves to greatly increase the magnetic flux but does not in any 
way interfere with its alternating properties, so that it increases 
and decreases and changes its direction in precisely the same 
manner as the flux that surrounds a single wire. The flux de- 



846 HANDBOOK ON ENGINEERING. 

veloped by A, swells out as indicated by the lines a a a and cuts 
through the side of the secondary coil B. If the circuit through 
this coil is close an alternating current will be generated in it, 
and this current will develop a magnetic flux that will swell out 
and cut the side of the primary coil A. The e.m.f. induced in 
A by the flux of B will be in opposition to the self-induction de- 
veloped by its own flux, hence, if the circuit through B is open, 
the current flowing through A will be small because the self- 
induction will counteract the impressed e m.f . so as to leave but 
a small effective e.m.f. As soon as the circuit through B is 
closed, the inductive action of this coil upon A will offset to a 
certain extent the self-induction and thus assist the impressed 
e.m.f. in forcing more current through A. The more the current 
through B is increased, the stronger its action upon A and as a 
result the more the self-induction of A will be neutralized and the 
stronger the primary current will become. This action which 
occurs in a perfectly natural manner serves to make the trans- 
former a self-regulating apparatus, so that if a strong current is 
required in the secondary circuit, a strong current passes through 
the primary so as to furnish the energy necessary to develop the 
strong secondary current. If no current is drawn from the 
secondary, the primary current is reduced to nearly nothing. 

To explain fully the action in a transformer would require a 
rather lengthy discussion of the principles involved, but the 
action, in a general way, can be made clear without going deeply 
into the theory. In explaining the phase relation of the current 
the self-induction and the impressed e.m.fs. in connection with 
Fig. 8 it was shown that the angle between the self-induction and 
the current is 90 degrees, and that the angle between the current 
and the impressed e.m.f. can be anything from zero up to nearly 
90 degrees. If the current is passed through transformers or 
other inductive devices, the current will lag considerably 
Suppose it lags 10 degrees, then the total angle between the lm- 



HANDBOOK ON ENGINEERING. 847 

pressed e.m.f. and the self-induction will be 100 degrees. Now 
in a transformer the e.ra.f. induced in the secondary coil is in 
phase with the self-induction in the primary coil, hence, with the 
above angles it would be 100 degrees behind the impressed e.m.f . 
in the primary coil. Now if the secondary current lags as much 
as the primary, it will be 110 degrees behind the primary im- 
pressed e.m.f. and the magnetic flux developed by this current 
will induce an e.m.f. in the primary coil 90 degrees behind 
itself or 200 degrees behind the primary impressed e.m.f. 
This e.m.f. induced in the primary coil by the action of the sec- 
ondary current not only counteracts the self-induction in the 
primary coil, but in addition changes. the phase relation between 
the primary current and its impressed e.m.f., making the angle 
smaller. This change in the phase relation between the current 
and impressed e.m.f. results, in turn, in a change of the phase 
relation of the secondary current, and this change in the phase of 
the secondary makes a corresponding change in the phase of the 
primary. If we were to trace up the action back and forth from 
primary to secondary currents we would finally arrive at 
the true phase relation of the currents and e.m.fs. in both circuits 
but this is a complicated and unnecessary process of reasoning. 
We can easily see that the current induced in the secondary coil 
will have a certain phase relation with respect to the primary 
current, and we can further see that the combined magnetizing 
effect of the two currents, the primary and secondary, is the 
same as that of a single current having a phase intermediate 
between the phases of these two. Following this course of 
reasoning we have only one inductive action to deal with and this 
is in such a phase relation that as it increases it decreases the self- 
inductive e.m.f. in the primary and thus permits more current to 
pass through this coil, and this increase in current in the primary 
causes a corresponding increase in the secondary current. When 
the secondary current is very small the self-induction in the 



848 HANDBOOK ON ENGINEERING. 

primary is very great and as a result the lag of the primary 
current is increased and its strength is decreased. As the sec- 
ondary current increases, the self-induction in the primary 
decreases, and the lag of the primary current reduces while 
the current strength increases. The strength of the secondary 
current is varied by varying the resistance in the secondary 
circuit ; if this resistance is reduced the current is increased. 

To make a transformer as perfect as possible it is necessary to 
place the primary and secondary coils in such a position that 
the mutual induction between them may be the greatest pos- 
sible, that is so that all the magnetic flux developed by 
the primary coil may cut through the secondary and all 
the flux of the secondary may cut through the primaiy. 
If the coils are arranged as in Fig. 30 it can be seen at once that 
all the flux of A will not cut through B and in like manner all the 
flux of B will not cut through A. It is not possibleto arrange 
the coils so that all the flux of one coil will pass through all the 
turns of wire on the other coil, but this condition can be very 
nearly realized. If one-half of coil A is wound on each side of 
the core C and then the B coil is wound in two parts directly 
over the A coils the chance for the flux of one coil to not pass 
through the other coil will be greatly reduced. 

The flux that does not pass through the opposite coil is called a 
leakage flux, thus in Fig. 30 the lines a that pass through coil 
A but not through B constitute the leakage from coil A and in 
like manner the flux of coil B that does not pass through A is 
the leakage of B. The leakage flux represents just so much mag- 
netism thrown away, hence the effort of the designer is to arrange 
the. coils so as to reduce it to the smallest amount possible. If 
the two coils were wound together, that is, if we took the wire»s 
and wound them side by side forming a single coil, the leakage 
would be practically nothing, but this construction cannot be used 
as with itjthere would be great danger of the insulation between 



HANDBOOK ON ENGINEERING 



849 



the coils giving away, and this would destroy the transformer. 
This form of winding can be approximated to by winding each 
coil in many sections and placing these in sandwich fashion upon 




JFl£Si 



the ircn core as is shown in Fig. 31 in which the sections forming 
one coil are shaded, and those of the other coil are not. This is 
the construction that is followed generally in large transformers. 
In the majority of designs, however, the primary and secondary 
coils are wound one over the other. 

Transformers are used for the purpose of changing the voltage 
of the current. The name transformer is misleading, as it creates 
the impression that the device transforms the current, when as 
shown in the foregoing it does nothing of the kind, it simply 
generates a secondary current which is in no way connected with 
the primary. When electric energy is transmitted to a consider- 
able distance by means of alternating currents, the voltage used 
is much higher than is required for the operation of lamps 
or motors, hence, at the receiving end of the line this cur- 
rent is passed through transformers and secondary currents are 
generated in these that are of the voltage desired. The voltage 

54 



850 HANDBOOK ON ENGINEERING. 

of the secondary current is controlled by the number of turns of 
wire placed upon the secondary coils. Roughly speaking, if 
the primary coil has ten times as many turns as the secondary 
the voltage of the secondary current will be one-tenth of that of 
the primary. If the primary voltage is 2000 and the secondary 
is 100 the primary coil will have twenty times as many turns of 
wire as the secondary. 

Transformers that deliver a secondary current of lower volt- 
age than the primary are called lowering transformers, while 
those that deliver a secondary of higher voltage are called raising 
transformers. For distributing current to consumers, lowering 
transformers are used. But in long distance transmission plants, 
where the current in the transmission line has an e.m.f. of any- 
where from 10,000 to 30,000 volts, raising transformers are 
used at the power house, and these take the current from the 
generators, which may be of 1,000 or 2,000 volts and deliver to 
the line a secondary current of 10,000 or more volts. 

Transformers cannot be used with continuous currents for the 
simple reason that as these currents do not fluctuate the magnetic 
flux developed by them remains stationary and, therefore, there 
is no inductive action. 

A medium size transformer is shown in Fig. 32. The com- 
plete transformer is seen at the right side of the illustration. In 
the center is shown the lower part of the iron core, with the wire 
removed from one leg, this wire being shown on the left. The 
iron plates at the bottom of the figure form the upper part of the 
iron core. 

The iron core of a transformer is built up out of sheet iron. 
It could not be made a solid mass, for, if it were, secondary cur- 
rents would be induced in it, and thus the energy in the primary 
current would be used up in developing useless currents with iron 
core. The sheet iron laminations are insulated from each other, 
so as to prevent the development of currents in the core. 



HANDBOOK ON ENGINEERING. 



851 



As can be seen from the illustration the wire wound on each 
leg of the core belongs in part to the primary and in part to the 
secondary circuit. If the primary wire is proportioned so that it 
is proper for a 1,000 volt current when the parts on the two legs 
are connected in series, then it can be made proper for 500 volts 




Fig. 32. 



by connecting the two parts in parallel. If the secondary coils 
will develop a voltage of 100 when both parts are connected in 
series, they will develop 50 volts if both parts are connected in 
parallel, but in this case the current will be doubled. 

The transformer as shown to the right in Fig. 32, is complete, 
but for the purpose of protecting the wire an outer casing is pro 



852 HANDBOOK ON ENGINEERING. 

vided. For high voltage transformers, this casing is made water 
tight and is filled with oil so as to improve the insulation of the 
apparatus. Very large transformers are provided with means for 
cooling them. In some, air is forced through the coils and iron 
core. In others, coils of pipe are placed within the casing and 
water circulates through these. 

Alternating 1 current generators. In alternating current gen- 
erators the field is magnetized permanently by means of a con- 
tinuous current. This current is obtained, generally, from a small 
continuous current generator that is called an exciter. Some alter- 
nators as a rule of small capacity are provided with a com mu- 
tator to rectify a portion of the current the machine generates so 
as to provide a continuous current to magnetize the field. An 
alternating current cannot be used to magnetize the field because 
the field magnetism must remain unchanged. 

Alternators are also arranged so that the field is magnetized 
by the combined action of the two continuous currents above 
mentioned, that is, by the current from a separate exciter and 
the current derived from the armature. Alternators excited in 
this manner are called compound machines and are the counter- 
part of the continuous current generator. Alternators that are 
excited by the current from a separate exciter alone are the coun- 
terpart of the plain shunt wound continuous current generator. 

There are several other ways in which the field can be magnet- 
ized to make an alternator of the compound type, and the most 
important of these will be found fully explained under the head- 
ing of "Compensated Generators." 

The object of compound winding in alternators is the same as 
in continuous current generators, that is, to keep the voltage con- 
stant and not allow it to drop as the current strength increases. 
Large alternators used in central stations are always of the com- 
pound type. 

The way in which alternating current generators act can be 



HANDBOOK ON ENGINEERING. 



853 



understood from the diagrams Figs. 33 to 37. In Fig. 33 P 
and N represent the poles of the field magnet of a two-pole 
machine. The armtaure is provided with a single coil of wire 
marked a. When this coil is in the position shown, no e.m.f. 
will be induced in it, but as it begins to rotate from this position 
an e.m.f. will begin to be induced, and this will increase in mag- 
nitude until one quarter of a revolution has been made, when it 
will be at the maximum value. During the next quarter revolu- 
tion the e.m.f. will gradually reduce, becoming zero when the 
half turn is completed. During the next half turn the e.m.f. will 
again rise to a maximum and fall to zero, but it will be oppositely 





Fie. 



Fig. 34. 




Fig 35 



directed, so that if during the first half turn the e.m.f. is posi- 
tive, during the next half it will be negative, and this operation 
will be repeated for each revolution of the armature. Thus it 
will be seen that if the armature revolves ten times in a second, 
the frequency of the current generated will be ten, and in any 
case the frequency will be equal to the number of revolutions the 
armature makes in a second. This is true for a two-pole machine, 
if the generator has four poles the frequency of the current will 
be equal to twice the number of revolutions per second and for 
any greater number of poles the frequency will be equal to the 
number of revolutions of the armature per second multiplied by 
half the number of poles. Alternating current generators are 
always made with a large number of poles so that the frequency 
required may be obtained without running the armature at too 
great a speed. 



854 HANDBOOK ON ENGINEERING. 

The diagram Fig. 33 illustrates a simple alternating current 
generator, or what is called a single-phase generator. A single- 
phase machine is one that has one coil on the armature for each 
pair of poles in the fields and generates one alternating current. 

Fig. 34 illustrates diagrammatically a two-phase generator. A 
two-phase generator is an alternating current generator that gene- 
rates two alternating currents that are out of phase with each 
other by one-quarter of a period, that is, by 90 degrees. Such a 
generator is provided with two coils or sets of coils for each pair 
of poles and these are placed at right angles to each other in a 
two-pole machine and so that the sides of one set come opposite 
the centers of the other set, in multipolar machines. 

In Fig. 34 it will be seen that coil a is in the same position as 
the coil in Fig. 33, hence no e.m.f. is being induced in it. Coil 
b, however, is in the position in which the induced e.m.f. is of the 
maximum value, thus it will be seen that as the armature revolves 
the e.m.f. in one coil will rise toward the maximum while that in 
the other coil will be decreasing toward zero. 

Fig. 35 illustrates a three-phase generator. A three-phase 
generator is a machine that generates three alternating currents 
that are out of phase with each other by an angle of 120 de- 
grees, or one-third of a period. Such a machine has three coils 
or sets of coils for each pair of field poles. 

In Fig. 35 it will be seen that coil a is in the position in which 
no e.m.f. is generated, and if we assume that the armature is re- 
volving in the direction of the hands of a clock, then the 
e.m.f. induced in coil b is very near the maximum value, but is 
still increasing, and will become the maximum when the coil 
reaches the horizontal position. In coil c the e.m.f. has passed 
the maximum and is reducing toward zero, which value it will 
reach when the coil reaches the vertical position, or the position 
in which a now is. 

If an alternator is of the multipolar type the coils will be dis- 



HANDBOOK ON ENGINEERING. 



855 



posed in the manner shown in Fig. 36. If it is a single-phase 
machine it will have one set of coils only, those marked A. If it 
is a two-phase generator it will have two sets of coils, the addi- 




tional set being placed in the position snown in broken lines and 
marked B. In this construction the machine appears to have as 
many A coils as there are poles and the same number of B coils, 
which is in contradiction to the statement made above that a single- 
phase machine has one coil for each pair of poles. The truth, 




Fig. 37. 



however, is that each coil in Fig. 36 is virtually one-half of a 
coil. Fig. 37 shows the way in which the coils are arranged in a 
three-phase generator of the multipolar type, the three sets of 
coils being marked ABC. In monocyclic generators the coils 



856 



HANDBOOK ON ENGINEERING. 



are arranged as in Fig. 36, but they differ from the two-phase 
winding in that the B coils are one-quarter the size of the A coils. 
In actual generators the armature coils are seldom given the form 
shown in these diagrams, but whatever the form may be the prin- 
ciple of winding is the same. 

In an alternator the armature coils forming one set are connected 
in series with each other, and the entering end of the first coil and 
the leaving end of the last coil are connected with collector rings 
mounted upon the armature shaft, and the current is taken from 
these by means of brushes similar to the commutator brushes of 




continuous current machines. In monocyclic generators one end 
of the B set of coils is connected with the middle point of the 
A set, and the three remaining ends are connected with col- 
lector rings. This is the arrangement with generators of 
what is known as the revolving armature type, which is the 



HANDBOOK OX ENGINEERING, 857 

one illustrated in Fig. 33 to 37. There is another type in 
which the outer part which is stationary is the armature and the 
revolving part is the field. Machines of this kind are called re- 
volving field alternators. The principle of operation is the same 
in both types, but the revolving field type has the advantage that 
as the armature is stationary, no collector rings and brushes are 
required to take off the current. All that is necessary is to pro- 
vide binding posts to which the ends of the armature coils are con- 
nected, and from these the external circuit wires are run off. 

A revolving" field alternator is shown in Fig. 38. In machines 
of this type, the field magnetizing coils are mounted on the 
periphery of the revolving part, hence the current that traverses 
them must pass through collector rings mounted upon the shaft. 
These rings are clearly shown in the illustration, the collector 
brushes being held, insulated from each other, by the, stand 
located in front of the rings. Thus it will be seen that this type 
of machine requires collector rings, just the same as the revolving 
armature type, but the difference between the two is. that in the 
latter the whole armature current passes through the collector 
rings, and on that account they must be made very large, while 
in the revolving field machines they can be made small, as only the 
field current passes through them, and this is only from one to 
two per cent of the armature current. 

There is still another type of alternating current generator in 
which the wire on the field as well as the armature is held station- 
ary. Such machines are called inductor generators. The revolv- 
ing portion of such generators is simply a mass of iron formed 
like a very large pinion with correspondingly large teeth. When 
this part revolves the ends of the teeth sweep over the armature 
coils, running as close to them as they can without touching. The 
magnetic flux developed by the field coil issues from the ends of 
the teeth and cuts through the armature coils thus inducing e.m.fs. 
in them . It will be seen that the difference between this type of 



858 



HANDBOOK ON ENGINEERING. 



generators and the revolving armature type is that instead of re- 
volving the armature coils through the stationary field flux, the 
latter is revolved and the armature coils are held stationary. The 




Fie-. 39. 



difference between the inductor generator and the revolving field 
type is that in the latter the field is magnetized by a number of 
coils and these are rotated together with the field poles, while in 
the inductor machine there is a single field magnetizing coil and 
this remains stationary, the part that revolves being what might 
be called the poles. 

An inductor alternator is shown in Fig. 39. The small 
machine mounted on the right side of the base is the exciter that 



HANDBOOK ON ENGINEERING. 859 

furnishes the field magnetizing current. The outer casing of the 
machine holds a ring built up of sheet iron laminations, which 
constitutes the armature and supports the armature coils. The 
large teeth, or polar projections which are well shown in the 
illustration are carried by the revolving part, and when rotating 
cause the magnetic flux to sweep over the armature coils. TJae 
field coil is placed back of these polar projections. 

Alternating current generators are run singly, or they may be 
connected in parallel, but they cannot be run in series. If an 
attempt is made to run them in series, one of the machines will 
act as a motor and will be driven by the current generated by the 
other. When alternators are connected in parallel it is necessary 
that they run at exactly the same velocity, if they are identical 
in construction. If the generators are not of the same construe^ 
tion then their velocities will depend upon the number of poles 
each one has. Machines of different size and even design, can be 
connected in parallel, providing the frequency of the currents 
they generate are the same. To make the frequency the same it 
is necessary that the velocity of each machine multiplied by the 
number of poles it has be equal to the same number. Thus if 
one machine has twice as many poles as the other, it must run at 
one-half the velocity. The velocity of alternators connected in 
parallel must be equal, absolutely, and not practically so ; that 
is, if two machines are alike, and one runs at 1000 revolutions 
per minute, the other must run at 1000 and it cannot run at 999 
or 1001. Since such extreme accuracy in speed is necessary it 
might be inferred that it is practically impossible to run alter- 
nators in parallel unless their shafts are coupled together, or they 
are connected through spur gearing with the same driving shaft. 
As a matter of fact, however, alternators can be run in parallel 
even if one is driven by a steam engine and the other by a water 
wheel, and they may be side by side or several miles apart. The 
reason why this is the case is that when the machines are in oper- 



860 HANDBOOK ON ENGINEERING. 

ation, the current holds them in step. If several generators are 
feeding into the same circuit, and one machine tends to lag 
behind the others, its current reduces and thus the speed in- 
creases as less power is required to drive it. If the tendency to 
lag increases, the machine begins to act as a motor, and is driven 
by the current from the other machines. 

While it is possible to run alternators in parallel under almost 
any conditions providing they are speeded so as to generate cur- 
rents of the same frequency and nearly the same voltage, entirely 
satisfactory results cannot be obtained unless the angular motion 
is uniform, that is, unless the velocity of rotation is the same at 
all points of the revolution. If a steam engine has a light fly- 
wheel the velocity of the shaft will not be the same at all 
points of the revolution, but will be the slowest when the 
crank is passing the center, and the fastest when at half stroke. 
This fact is clearly shown by the irregular motion of the 
paddle-wheels of river boats driven by a single engine. 

If two alternators are driven by two engines whose rotative 
motion is not uniform and the engines are so timed that one 
is on the center when the other is at half -stroke, then the 
action of the two alternators will be irregular, for when one 
machine is rotating at the highest velocity the other will be ro- 
tating at the lowest. This uneven action of the alternators may 
be compared with the work of two horses hitched to a wagon and 
pulling unevenly. If both horses pull together all the time the 
whiffle-tree will remain straight and the wagon will be drawn 
along smoothly ; but as soon as the horses begin to pull unevenly 
the whiffle-tree will be jerked back and forth and the motion of 
the wagon will be irregular. In this case the horses soon tire 
out because they work against each other part of the time. The 
action between two alternators that do not rotate with uniform 
velocities is practically the same as that of two horses that do 
not work together ; the machine that runs ahead not only sends a 



HANDBOOK ON ENGINEERING. 861 

U 

current into the main circuit, but in addition backs up a cur- 
rent through the other generator, thus wasting energy by 
causing a strong current to flow back and forth between the two 
machines. To overcome this difficulty engines made to drive 
alternators are provided with extra heavy flywheels, so that the 
momentum may be sufficient to keep the speed up to the normal 
point while the crank is passing the center. 

With small alternators that have only a few poles and are 
driven by high-speed engines, the effect of irregular motion is not 
so great as in large machines having many poles, hence the large 
slow-speed engines used to drive alternators having a large num- 
ber of poles, must be provided with excessively large flywheels to 
run in a satisfactory manner. 

The reason why alternators with a large number of poles require 
greater regularity in motion to give satisfactory results, can be 
easily understood. Suppose we have a pair of two-pole machines 
driven by engines whose flywheels are 25 ft. in circumference. 
Suppose, further, that the irregularity in motion is such that each 
engine when running at the faster velocity, gets three inches ahead 
of the other. Then the advance in position will be one per cent, 
and consequently the currents of the two generators will run 
ahead and behind each other one per cent at each quarter of a 
revolution. Now, if these same two engines drive two twenty- 
pole alternators, then the irregularity in motion will be multiplied 
ten times, because one-tenth of a revolution will give one cycle of 
current, and the current of each machine will run ahead and fall 
behind the other ten per cent, instead of one per cent. 

Starting alternators connected in parallel : — In starting con- 
tinuous current generators that are connected in parallel all we 
have to do is to set one machine in operation and then after the 
second one is running up to full speed, we adjust its field regu- 
lator until the voltage is the same as that of the first machine, or 
one or two volts higher. We then throw the switch and connect 



862 HANDBOOK ON ENGINEERING. 

it with the switchboard. In starting alternators that are con- 
nected in parallel we have to do more than this, we must not only 
adjust the second machine so that its voltage is the same as that 
of the first, but we must bring it up to the proper speed and get its 
current in phase with that of the first generator before we connect 
it with the switchboard. To accomplish all this with certainty, 
devices are used that are called synchronizers, or phase indicators. 
These devices consist generally of a couple of small transformers 
one of which is connected with the circuit of each generator. The 
secondary wires of these transformers are connected with each 
other and one or two incandescent lamps are connected in this 
circuit. When the second machine is started up, as its speed is 
much lower than that of the generator already in operation the 
frequency of the secondary current of its transformer will be much 
lower than that of the first machine, and as a result the lamps in 
the circuit of the two transformers will flicker rapidly. As the 
second machine builds up its speed the flickering of the lamps 
will become slower. When the two generators are running at 
nearly the same speed the flickering will be replaced by rather 
long periods of darkness and light. During the periods when the 
lamps are lighted the current generated by one of the transformers 
is in such a direction as to act in series with the current of the 
other and thus draw the current through the lamp. When the 
lamps are dark it is because the currents of the two transformers 
are in opposition to each other and thus no current passes through 
the lamps. The second generator is connected with the switch- 
board during one of the periods of darkness or- brightness, de- 
pending upon the way in which the transformers are connected. 
The second generator will not be running at exactly the proper 
speed when it is connected with the switchboard, but as soon as 
it is connected the currents of the two machines acting upon each 
other will at once draw the second machine into step with the 
first one, and they will continue to run in step even if the power 



HANDBOOK ON ENGINEERING. 



863 



driving one of the machines should fail. In the latter case, the 
first machine would not only furnish current for the main cir- 
cuit, but would in addition drive the second machine as a motor. 
The way in which synchronizing lamps are connected in single 
or polyphase circuits is clearly illustrated in the diagram Fig. 40. 



To Bus Bars. 



Synchronizing 

Lamps. 



|Transformers | — i — <' N - '\\ — — -® 

Tempor ary 
Switchboard^ rj ^Transformers 

TRS.r. Switch. 
□ □ 



/\ f\ 



7b GeneraCor. 
Fig. 40. 



The three upper lines are connected with the main bus-bars on 
the switchboard and the lower lines run to the generator that is to 
be synchronized. The left side of the diagram shows the connec- 
tions for synchronizing a single-phase generator. In such a case, 
the middle wire running to the bus-bars and to the generator would 
not be used. The synchronizing transformers would have their 
primary coils connected with the side wires in the manner shown 
by lines// and g g. When the generator current is in synchro- 
nism with that in the bus-bars, the primary currents in the two 
synchronizing transformers will flow in the direction of the arrows 
a a, and the secondary currents will be in the direction of arrows 
c, that is, in opposition to each other, so that no current will pass 
through the synchronizing lamps. If the connections of one of 



864 HANDBOOK ON ENGINEERING. 

the transformers are reversed, either in the primary or secondary, 
the two secondary currents will flow through the lamps in the same 
direction as indicated by the arrows d on the right side of the 
diagram. Thus it will be seen that the synchronizing lamps can 
be arranged so that they will light up when the generator current 
is in phase with the bus-bar current, or they may be arranged so 
as to be dark at this instant. Generally they are arranged so as 
to be bright when the current is in phase and the switch connect- 
ing the generator with the switchboard is closed at the instant 
when the lamps appear to be brighter. 

When two and three-phase generators are started up the first 
time a temporary synchronizing arrangement is connected in the 
manner shown on the right side of Fig. 40. The synchronizing 
lamps on the left side will show that the current flowing in the 
two side wires is in synchronism, but this does not show that 
the other currents also synchronize. To make sure that the 
temporary transformer is properly connected the connections e 
are made first, and if the lamps on both sides of the diagram 
become dark and bright together, the connections are correct. 
The connections are then broken and are transferred to the middle 
wire ; then when all the currents are synchronized, all the lights 
will light up together. Generally the internal connections of 
synchronizing transformers are properly made, and the correct 
connection of the terminal wires is clearly indicated so that mis- 
takes in making connections are not very liable. 

Compensating and compounding alternators* — Continuous 
current generators are provided with a compound field winding 
for the purpose of maintaining the voltage uniform as the arma- 
ture current increases. Alternating current generators are 
compounded for the same purpose. If the field of an alternator 
is excited by a current derived from an exciter the voltage of 
the machine will drop as the strength of the current generated in 
the armature increases. A part of the drop is due to the fact 



HANDBOOK ON ENGINEERING. 865 

that the increased current absorbs more voltage in passing through 
the armature coils. The balance of the drop is produced by 
the reaction of the armature current upon the field. As the 
current of the exciter that magnetizes the field remains constant, 
the magnetization produced by it remains constant. The cur- 
rent flowing in the aternator armature acts to demagnetize the 
field, and, as its action increases as the strength increases it 
follows that the stronger the current becomes the weaker the 
field will be, and, as a result, the lower the voltage of the cur- 
rent generated in the alternator armature. 

If a portion of the current of the alternator armature is recti- 
fied by being passed through a commutator and is used to assist 
the exciter current to magnetize the field then the field magnetism 
will increase as the armature current increases, because the 
action of the rectified current will increase. Thus by the com- 
pound action of the exciter current and the rectified armature 
current, the magnetism of the field of the alternator can be made 
to increase as the armature current increases, and in this way the 
voltage is increased so as to compensate for the greater drop of 
voltage on the armature coils, the result being that the voltage 
impressed upon the wire remains practically the same for all 
strengths of current. 

The above results can be obtained providing the phase relation 
between the current and the impressed, or line e.m.f. does not 
change ; but if the phase relation is continually changing such 
perfect regulation cannot be realized. The reason why changes 
in the phase of the current interfere with the regulation is that 
the same strength of armature current will produce different de- 
grees of reaction on the field magnetism with different phase 
relations. If the lag of the current is increased the reaction upon 
the field will be increased, and in like manner a decrease in the 
lag will reduce the reaction upon the field. Several arrangements 
are used for obtaining field magnetizing currents that will com- 

55 



866 HANDBOOK ON ENGINEERING. 

pensate for variations in the lag of the current as well as for va- 
riations in strength. Alternators provided with such arrange- 
ments are called " Compensated Generators." The way in which 
a field magnetizing current is obtained that will compensate for 
variations in lag as well as in current strength is by using a por- 
tion of the armature current to vary the strength of the current 
generated by an exciter, the exciter being provided with coils 
through which the current taken from the armature is passed. 
These coils are so disposed that their governing action upon the 
exciter is proportional to the lag of the current as well as its 
strength, hence the current that the exciter sends through the 
field coils of the alternator is at all times sufficient to compensate 
for variations in the strength and phase of the armature current. 

If an alternator is single-phase, one commutator is sufficient to 
rectify the portion of the armature current and to magnetize the 
field. For a two-phase machine, two commutators are required 
and for a three-phase, three commutators. To obviate using 
two and three commutators in polyphase generators, trans- 
formers are employed, two transformers for two-phase and 
three transformers for three-phase. The recording currents 
of these transformers are combined into one, and this com- 
bined current is passed through a single commutator to be recti- 
fied. In some cases only one of the currents of a two or three- 
phase generator is rectified, but with most machines, if they are 
connected in parallel, care must be taken to have the circuits 
from which the rectified current is taken properly connected with 
each other ; if not, one armature will short circuit the other. 
This is due to the fact that when alternators are run in parallel 
the rectified currents for the field coils are connected with each 
other through equalizer wires, in a manner similar to that used 
with continuous current generators. 

The ordinary connections for two generators in parallel are 
shown in the diagram Fig. 41. 



HANDBOOK ON ENGINEERING. 



867 



As will be seen, the field-magetizing currents derived from the 
commutators are connected with each other through the equalizer 
switches, hence, to avoid short circuiting the armature through the 
equalizer connections, if the commutator rectif} r one current only, 



CONNECTIONS OF COMPOSITE FIELD ALTERNATING GENERATORS 

FOR RUNNING IN MULTIPLE 




Fig. 41. 



the two rectified currents must be in phase with each other. The 
rheostats shown in each field circuit are for the purpose of 
adjusting the voltage of each generator independently. 

The use of transformers to transform the portion of the arma- 
ture current that is rectified is no objection against polyphase 
machines, because, even with single phases, the armature voltage 
is generally so high that a transformer is used so as to ©btain a 
secondary current of low voltage to pass through the field coils. 

Alternating Current Motors* — From the foregoing it can be 
understood that an alternating current generator can be used as 
a motor providing it is supplied with the same kind of currents, 



$03 HANDBOOK ON ENGINEERING. 

that is, with a continuous current to magnetize the field, and with 
an alternating current for the armature. A single-phase alter- 
nator will run as a motor if connected in a single-phase circuit. 
Two-phase generators will act as two-phase motors, and three- 
phase generators will act as three-phase motors. With either one 
of these three types of machines a continuous current will 
be required to magnetize the field. Two and three-phase ma- 
chines can be run with a single alternating current, by connect- 
ing one of the armature circuits only, or all the circuits may be 
used if they are connected in parallel. 

When an alternator is used as a motor it is called a synchro- 
nous motor, because it runs in synchronism with the generator 
that supplies the current. A simple alternator (single-phase ma- 
chine) becomes a single-phase synchronous motor, and a two 
or three-phase generator becomes a two or three-phase syn- 
chronous motor. 

A single-phase synchronous motor will not start up of its own 
accord, but must be set in motion and run up to nearly its full 
speed before it will begin to act as a motor. If it is started up 
without a load when it comes rather near to its full speed it will 
give a sudden jump and swing into step with the current and then 
continue to run at this velocity. If it is started with a full load 
it will not fall into step with the current until its speed is very 
nearly up to the proper point. Synchronous motors are neveV 
started under load, they are always started light. 

Two and three-phase synchronous motors can be started with- 
out outside assistance. Synchronous motors are generally pro- 
vided with a self-starting motor, to set them in motion, or else 
they are arranged so as to be self-starting by being converted, 
jn the act of starting, into some form of motor that is self- 
starting. 

Fig. 42 shows a synchronous motor of large size provided 
with an induction motor of much smaller capacity to start it. 



HANDBOOK ON ENGINEERING. 



8<)9 



This motor is of the revolving field type, and, as will be seen, is 
precisely the same as the same type of generator. 




1000 h. p. two-phase 



REVOLVING- FIELD SYNCHRONOUS MOTOR. 

Fig. 42. 



Owing to the fact that synchronous motors are not self -starting, 
they are generally used only where large power is required, unless 
they happen to be made so as to be self -starting, then they are 
used in small sizes. 

A synchronous motor, when running, will keep in step with the 
current, no matter how much the load may vary, provided it is 
not made greater than the capacity of the machine. If the load 
is made so great that the motor cannot carry it, the armature 
will be pulled out of step with the current and will imme- 
diately come to a stop. On this account, motors of the 
synchronous type are not well adapted to operate cranes or similar 
machines in which there is a liability of greatly overloading the 
machine occasionally. 



870 HANDBOOK ON ENGINEERING. 

The current developed by an alternating current generator will 
lag behind the impressed e.m.f. as has been fully explained in the 
foregoing. If this currentis passed through a second machine, that 
acts as a motor, the latter will tend to generate a current that flows 
in opposition to that of the generator ; hence, in this current the lag 
will be in the opposite direction of that of the current that drives 
it. That is when the machine acts as a motor its whole action as 
a generator is reversed. Owing to this fact, if a synchronous 
motor is placed at one end of a circuit, and a generator at the 
other, the motor will act to neutralize the self-induction of the 
generator, and thus to bring the current in the circuit, and the 
impressed e.m.f. into phase with each other. Thus, a synchro- 
nous motor can be made to act in the same way as a condenser, 
to reduce the lag of the current. 

Power f actor* — In an alternating current circuit, it is very 
important to reduce the lag of the current as far as possible 
because the actual amount of energy carried by the current depends 
upon the angle of lag, as was fully explained in connection with 
Figs. 23 to 25. In a continuous current circuit the power is 
always equal to the product of the volts by the amperes, 
but in an alternating current circuit this product is not a 
measure of the power. It is called the apparent power, or the 
volt-amperes. The actual power is equal to the amperes multi- 
plied by the e.m.f. in phase with the current, or the active voltage, 
as it is called. The ratio between the true power and the volt- 
amperes is called the power factor. The power factor can be 
obtained by dividing the true power by the volt-amperes, and it 
may range from 100 per cent when the current and impressed 
e.m.f. are in phase down to five or ten per cent when the angle of 
lag is nearly 90 per cent. In actual working circuits the power 
factor ranges between about 95 and 75 per cent. Any kind of 
device that has a low reactance, as, for example, incandescent 
lamps, acts to keep the angle of lag of the current small, and thus 



HANDBOOK ON ENGINEERING. 871 

the power factor high. Devices having large reactance, such as 
transformers, and induction motors act to increase the angle of 
lag of the current, and thus to reduce the power factor. Devices 
that develop a negative reactance, that is, which cause the current 
Ito lead the impressed e.m.f.,- such as condensers and synchronous 
motors, can be used in circuits in which transformers and similar 
devices are operated so as to counteract these and thereby keep 
up the percentage of the power factor. 

Induction and other types of motors* — In addition to the 
synchronous motors just explained, the only type of machine that 
requires notice here is the induction motor. This is by far the 
most extensively used of all alternating current motors, and from 
the manner in which it acts it has a greater range of adaptability 
than any other type. It may be well to mention here, however, 
that a plain motor, such as those used with continuous currents, 
can be made to operate with alternating currents providing the 
field cores are made laminated, instead of solid castings. If the 
field is solid the motor will not run if connected in an alternating 
current circuit because the large mass of iron constituting the field 
cannot be magnetized and demagnetized as fast as the current 
alternates. If we take hold of a freight car and try to shake it 
we will fail in the effort, simply because the bulk is too great to 
be set in motion rapidly. If, however, we take hold of the side 
of a light buggy and shake it we will be able to produce a very 
vigorous movement, simply because the bulk is light. In the 
same way, if we attempt to alternate the magnetic polarity of 
large masses of iron >re fail because the bulk is too great, but if 
ve divide the mass up Into many thin sheets we will have no diffi- 
culty in causing its polarity to change rapidly. Alternating cur- 
rent motors of this kind which are called commutator motors, 
kfcve been made, but they are not used or manufactured for com- 
mercial purposes at the present time, because they are far inferior 
to other types. They are open to two objections, one of which 



872 



HANDBOOK ON ENGINEERING. 



is that they spark considerably and the other is that they will not 
give much more than one-third the power that the same machine 
will develop if supplied with a continuous current. The reason 
why they give such small power is that on account of the many 
turns of wire on the field the inductive action is very great, hence 
the reactance is very high, and as a result the current lags exces- 
sively so that the power factor is very low, therefore, although the 
current is strong, the actual energy carried by it is comparatively 
small. Several other types of alternating current motors have 
been devised, but they have never got beyond the experimental 
stage. 

Principle of the induction motor- — Induction motors are 
made for single and polyphase currents. When in operation the 





Fig. 43. 



Fig. 44. 



principle of action is the same in all, but in the act of starting the 
single-phase machine is different from the others. Single-phase 
induction motors will not start of their own accord unless provided 
with special starting arrangements. The most common way of 
arranging a single-phase induction motor so as to be self-starting 
is to provide a set of starting coils that virtually convert it into a 



HANDBOOK ON ENGINEERING. 873 

two-phase machine in the act of starting. When the motor is 
under way the starting coils are cut out, although in some cases 
they are left in circuit all the time. The principle of the induc- 
tion motor can be explained by the aid of the diagrams Figs. 
43 to 46. These diagrams illustrate the action in a two-phase 
machine which is the one most easily understood. The 
single-phase induction motor is the most difficult one to ex- 
plain or to understand, so we will leave it for the 
last. In an induction motor, the stationary part, which is 
called the stator, and sometimes the field, is provided with coils 
that are connected with the operating circuits. The rotating part 
which is called the rotor and sometimes the armature, is provided 
with coils that are short circuited upon themselves and are not 
connected with the operating circuits. The principle of operation 
generally stated is that the currents in the stator develop an in- 
ductive action upon the coils of the rotor thus developing currents 
in these, the action being substantially the same as that in a 
transformer. On that account the stator is also called the 
primary member, while the rotor or armature is commonly called 
the secondary member. The primary currents passing through 
the coils of the stator, develop a magnetic flux and the secondary 
currents induced in the coils of the rotor also develop a magnetic 
flux, these two fluxes are at an angle with each other, and, hence, 
there is a strong attraction exerted between them, the magnetism 
of the rotor making an effort to place itself parallel with that of 
the stator. The magnetism of the stator rotates, on account of 
being developed by alternating currents , and the magnetism of 
the rotor in trying to place itself parallel with that of the stator 
also rotates, chasing the latter around the circle but never 
overtaking it. 

In Fig. 43 let A A represent two coils connected in one of the 
circuits of a two-phase system, and let B B represent two other 
coils connected in the other circuit of this same system . Suppose 



874 



HANDBOOK ON ENGINEERING. 



we consider the instant of time when the current flowing through 
the A A coils is at its maximum value, then at this very same instant 
the current in the B B coils will be zero. The current in the A A 
coils is then the only magnetizing current acting uj^on the ring at 
this instant. Suppose the direction of the current through A M 
is such as to develop a magnetic flux that will traverse the space 
in the center of the ring in the direction of arrow C. As the 
current in the A A coils begins to decrease, that flowing in the 
B B coils will begin to increase. Let the direction of the current: 
in the B B coils be such as to send a magnetic flux through the 
center of the ring in the direction of arrow C in Fig. 45. This 
magnetization will act upon that developed by the current in the 
A A coils and will have a tendency to twist it around into the 
direction of arrow C in Fig. 44. When the current in the^. A 
coils has reduced and the current in the B B coils has increased 
until they are both equal, then each one will act with equal force 




.Fiff. 45. 




Fig. 46. 



to establish a magnetization in its own direction , and the resul 
will be that the actual direction of the magnetic flux will be as 
iDdicated by arrow C in Fig. 44. Thus we see that by the 
decrease in the strength of the current in the A coils and the 



, 



HANDBOOK ON ENGINEERING. 875 

increase in the strength of the current in the B B coils until they 
are both equal, the magnetic flux has been rotated from the 
position of arrow G in Fig. 43 to its position in Fig. 44. Now 
as the variation in the currents progresses, and that in A A 
becomes weaker, while that in B B becomes stronger, the 
direction of the magnetic flux will be still further rotated so that 
when the current in B B reaches the maximum value, and that in 
A A becomes zero, the direction of the flux will be that of arrow 
G in Fig. 45. As we advance beyond this instant of time, the 
current in B B will begin to reduce, while that in A A will begin 
to increase, but its direction will be the opposite of what it was 
in Fig 43, so that when the currents in the two sets of coils 
become equal again, the direction of the magnetic flux will be 
that of arrow G in Fig. 46. When the current in the A A coils 
reaches the maximum and that in B B becomes zero, the flux will 
have rotated through one-half of a revolution and arrow G will 
be in the vertical position but pointing downward. 

If we follow the action of the currents further we will find that 
as a result of the continuous increasing and decreasing and 
changing of direction, the magnetic flux indicated by arrow C 
will continuously rotate keeping time with the frequency of the 
currents. Now if we suppose that an armature upon which a 
number of coils are wound in a diametrical position, is placed 
within the field ring, and is held stationary, we will see at once 
that the rotating magnetic flux will cut through its coils and 
develop e.m.fs. in them. The currents developed in these coils 
on the stationary armature will be alternating, hence, they will 
develop a magnetic flux in the armature that will rotate, and 
keep time with the rotating flux developed by the field coils. 
Both these fluxes act inductively upon the field and armature 
coils, their combined effect being equal to that of a single flux 
located 90 degrees in advance of the e.m.f. induced in the 
armature coils, hence, somewhat more than 90 degrees ahead of 



876 HANDBOOK ON ENGINEERING. 

the armature current. If we hold the armature by means of a 
brake, and free this slightly, so that the armature may revolve j 
slowly, it will at once follow around after the rotating field, but | 
as its magnetization is developed by currents that are induced by 
the action of the field magnetism, it will matter little how fast 
the armature may revolve, its magnetization will never be able to 
overtake that of the field. - 

As can be judged from the foregoing explanation, an induction 
motor is not a synchronous machine, and its armature can never at- 
tain a velocity equal to that of the rotating field. If the resistance 
of the armature coils is made very low, it may reach a velocity 
very near to that of the rotating flux. The difference between the 
velocity of the rotating flux and that of the rotating armature is 
called the slip of the motor. 

If the motor is designed for constant speed, the resistance of 
the armature coils is made very low, and then when the machine is 
running free, the speed of the armature may run up to 99 or 99J 
per cent of the speed of the rotating field, and when the maximum 
load is put on it may not drop lower than 94 or 95 per cent. If 
a motor is designed in this way the pull of the armature when it 
starts up will be small and will gradually increase until the speed 
is about nine-tenths of the maximum when it will again begin to 
decrease. 

If it is desired to make a motor that will give a strong pull 
when it starts up, its armature coils must have more resistance, 
and then it will pull harder on the start, but as fast as the speed 
builds up the pull will reduce. From this it will be seen that in- 
duction motors that are made so as to run at nearly a constant 
speed, say to vary five or six per cent between full load and run- 
ning free, will not give a strong pull in the act of starting, hence 
they will have to be started without a load. If a motor is to be 
made to start under a full load it must be proportioned so that it 
will not run at a constant speed, but will gradually reduce its 
velocity as the load is increased. 



HANDBOOK ON ENGINEERING. 877 

Induction motors, if very small, are started by connecting 
them directly with the operating circuits, but if they are of any 
capacity they must be provided with some kind of starting resist- 
ance so as to keep the starting current down within safe limits. 
One way of starting is to introduce resistance into the primary 
circuits, but this results in reducing the strength of the 
field, and thus the pull of the armature. Another way is to intro- 
duce resistance into the armature coil circuit. This is the best 
method, because it enables the motor to start up with a strong 
pull. 

Three-phase induction motors act in precisely the same way as 
the two-phase, the only difference being that the rotation of the 
field flux is produced by the increase and decrease in the strength 
of three currents flowing through three sets of coils equally 
spaced around the circle instead of by the increase and decrease 
in two currents flowing in two sets of coils equally spaced around 
the circle. 

In the single-phase induction motor, the magnetic flux developed 
by the single alternating current traversing a single set of coils on 
the field combines with the magnetic flux developed by the armature 
current, to develop a rotatingfield and this acting upon the armature 
coils produces rotation in precisely the same way as in the two- 
phase machine. This is the action that takes place after the 
armature is set in motion, but if the load is increased and the 
armature speed is reduced the rotating field begins to become 
irregular, and by the time the armature velocity is reduced to 
about one-half, the rotating flux becomes so irregular in its move- 
ment, that the armature pull begins to reduce very rapidly, and 
the machine comes to a standstill. Owing to this fact single- 
phase induction motors cannot be used in cases where it is de- 
sired to start with a strong pull, or where a wide range of speed 
variation is desired. 

To make a single-phase induction motor self -starting, it is wound 



878 HANDBOOK ON ENGINEERING. 

with two sets of coils, like the diagrams Figs. 43 to 46, and the 
current from the single-phase circuit is passed through these two 
sets of coils in parallel branches, and in one of the branches the 
reactance is greatly increased, so as to make the current in this 
branch lag much more than in the other. In this way a phase 
displacement is obtained between the two currents, and this pro- 
duces a corresponding displacement in the magnetic fluxes devel- 
oped by the two sets of coils, so that their combined action 
develops a rotating field. This field does not rotate at a uniform 
rate, like the field of a two-phase motor, but it is uniform enough 
for the purpose of setting the machine in motion. To increase 
the reactance in the auxiliary starting coils, all that is necessary 
is to wind them with many turns of fine wire, and this is an 
arrangement very commonly employed, but, in some cases, sep- 
arate coils are placed in the auxiliary circuit to obtain the required 
reactance. 

There are other ways in which single-phase induction motors 
are made self -star ting, but they are not very extensively used. 

While induction motors are very satisfactory machines, being 
adapted to every kind of work, even to the operation of railway 
cars, they have the objection of being highly inductive devices 
that act to greatly increase the lag of the current, and thereby to 
reduce the power factor. On this account they are often used in 
connection with synchronous motors so that the latter may coun- 
teract their inductive effect, and thus keep the power factor high. 

The small motor shown in Fig. 42, is an induction motor. 
Induction motors are made in many different designs, and as 
large as 300 to 400 H. P., but as a rule they are confined to much 
smaller capacities ; synchronous motors being used for the large 1 ' 
sizes. 

Rotary transformers and rotary converters* — A rotary 
transformer is a machine by means of which a continuous current 
may be obtained from an alternating current. A rotary con- 



HANDBOOK ON ENGINEERING. Oi9 

verter is a machine for accomplishing the same result. The 
essential difference between the two is that the first is driven by 
an alternating current and generates a continuous current, while 
the second changes an alternating into a continuous current. As 
a result of this difference the rotary transformer can be used to 
obtain a continuous current of any desired voltage from an 
alternating current of any given voltage ; but in the rotary con- 
verter, as the action is to convert the alternating into a con- 
tinuous current, the voltage relation is fixed so that for a given 
alternating current voltage we will get a corresponding contin- 
uous current voltage. Both these machines can be used in the 
reverse order, that is to transform or convert a continuous into an 
alternating cuurent. 



6 o 




i 



a 



a 



Fig. 47. 



Principle of the rotary transformer* — The principle of the 
rotary transformer is illustrated in Fig. 47. In this diagram A 
represents a continuous current armature, and B is an alternating 
current armature. If both these are provided with suitable 
magnetic fields then if continuous current is passed through A it 
w r ili become a motor and will drive B and generate therein a 
single alternating current or a number of them according to the 
way in which the armature is wound. Thus B may become a 
single or a polyphase generator. It can further be seen that the 



880 



HANDBOOK ON ENGINEERING. 



voltage of the currents generated by B is in no way connected 
with the voltage of the current that drives A, and depends wholly 
upon the way in which B is wound. If B is connected with an 
alternating current circuit, then it will run as a synchronous 
motor and drive A and the latter will generate a continuous 
current. This machine if driven by a continuous current will be 
self -starting, but if driven by an alternating current it will have 
to be started. If driven by an alternating current its speed will 
be controlled by the frequency of the current, but if driven by a 
continuous current its speed will vary with the magnitude of the 
load placed upon it. 




C C 



js 



a a 




Fig. 48. 



Fig. 49. 



Figs. 48 and 49 illustrate the principle of operation and the 
construction of a rotary converter. The armature A is of the 
continuous current type, having a commutator C. If it is a two- 
pole machine, then if wires are connected with diametrically 
opposite segments of the commutator as is indicated in Fig. 49 
by the arrows, and these are connected with the collector rings 
a a, brushes c c placed on these rings, will take of a true alter- 
nating current if the armature is placed in a suitable field and is 
driven. While alternating current can be taken from the brushes 
c c, a continuous current can also be taken from the brushes b b 



HANDBOOK ON ENGINEERING. 881 

which bear upon the commutator C. Thus, this machine, if 
driven, becomes a combination generator which will deliver a 
continuous and an alternating current at the same time. 
Machines of this type are constructed and are called double 
current generators. 

If the brushes c c are connected with a single-phase circuit, 
and the armature is placed in a suitable field, it will rotate and 
from the b b brushes of the commutator a continuous current 
can be drawn. If the brushes b b are connected with a continu- 
ous current circuit, an alternating current will be delivered 
through the brushes c c. 

If four wires are connected with four commutator segments one 
quarter of the circumference apart, and these are connected with 
four collector rings, then from these rings two alternating cur- 
rents 90 degrees out of phase can be obtained. Thus, with four 
connections with the commutator segments the machine can 
convert two phase currents into one continuous current, or one 
continuous current into two phase currents, thatis into two alter- 
nating currents 90 degrees out of phase. 

If wires are connected with three commutator segments one- 
third of the circumference apart, and these are connected with 
three collector rings, then the machine will become a three-phase 
converter, and if connected with a three-phase system will deliver 
one continuous current or if connected with a continuous current 
circuit will deliver the three currents of a three-phase system. 

The rotary converter, as will be seen from the foregoing, 
actually changes a continuous current into one or more alternat- 
ing currents, or one or more alternating currents into one con- 
tinuous current, and in every case there is a direct electrical con- 
nection between the continuous and the alternating current cir- 
cuits. As this type of machine simply converts the current of 
one type into current of the other type it is quite evident that 
there must be a fixed relation between the strength of the alter nat- 

56 



882 HANDBOOK OX ENGINEERING. 

ing and continuous currents and also between the voltages. An 
alternating current if of the sine type, will have an effective value 
of 70.7 per cent of its maximum value, for the amperes as well as 
the volts. So that if we have a continuous current of 70.7 
amperes and 70.7 volts, we must have an alternating current of 
100 amperes maximum value and 100 volts maximum value to be 
equal to it, and if the energy is also to be equal, the current in 
the alternating current circuit must be in phase with it e.m.f., 
that is the power factor must be 100. 

In a rotary converter the voltage of the continuous current is 
equal to the maximum voltage of the alternating current and the 
strength of the continuous current is equal to one-half the maxi- 
mum strength of the alternating current. Thus if the maximum 
voltage of the alternating current is 1,000 volts, the voltage of the 
continuous current will be 1,000, and if the maximum strength of 
the alternating current is 100 amperes the strength of the contin- 
uous current will be 50 amperes. This arises from the fact that 
the rotary converter does not develop energy, as it drives itself, 
hence, the energy in the continuous current cannot be more than 
that in the alternating, in fact it will be a trifle less owing to the 
energy absorbed in driving the machine. Now if the alternating 
e.m.f. and current have the maximum values of 1,000 volts and 
100 amperes, their effective values will be 707 volts and 70.7 
amperes, and the product of these two will be the energy in watts. 
Thus 707 X 70.7 = 50,000 watts. Now if the voltage of the 
continuous current is 1,000, its strength must be 50 amperes, less 
the amount absorbed in overcoming the friction of the machine. 

Fig. 50 shows a rotary converter of large size. 

Alternating Current Distributions* — The principal advantage 
of alternating over continuous currents is that they can be used 
for transmitting energy to much greater distances, owing to the 
fact that a high voltage can be used to transmit the main current 
over the wire, and at the receiving end this current can be passed 



HANDBOOK ON ENGINEERING. 



883 



through transformers, from which secondary currents of low volt- 
age may be obtained. In a few instances, low voltage alternating 




ROTARY CONVERTER. 

Fig. 50. 

currents are used for distributing current over small areas. The 
general arrangement of circuits and apparatus for a three-phase 
system of this kind is illustrated in the diagram Fig. 51. 




Fig. 51. 



The generator is shown at the extreme left. At a an induction 
motor is connected with the circuit. At b an " arc" light is 
connected in the secondary circuit of a small transformer. At c 



084 HANDBOOK ON ENGINEERING. 

a number of incandescent lamps are connected. At d the circuit 
is used to drive a rotary transformer, which develops a continuous 
current to charge storage batteries at e. The three solid line 
wires constitute the main circuit and all the apparatus is 
connected with them. The broken line above these is the 
neutral wire and is connected with the incandescent lamps 
only. If the number of these lamps in each circuit is the 
same, as is shown on the diagram, no current will pass to the 
neutral wire, but if in one of the circuits there are more lamps 
than in the other, the excess of current will pass to or from the 
neutral wire. Systems of this type are operated at voltages rang- 
ing between 200 and 600. 




Fig. 52. 



The diagram, Fig. 52, shows the way in which the circuits are 
arranged when the distance of transmission is from one to three 
or four miles. For such cases, the voltage generally used is 
2300. The .generator at the left develops currents that pass 
directly to the main line. At a an induction motor is connected 
directly to the main line. At b transformers are used to develop 
secondary currents of low voltage to supply the circuit wires c 
from which the motor d and incandescent lamps e are fed. At/ 
a series transformer is used to develop a secondary current o^ 
constant strength to operate the arc lamps g. The difference be- 
tween a series transformer and the ordinary type is that the 
former is provided with a mechanical regulator, actuated by the 
current which maintains the secondary current of constant 
strength and varies the voltage in accordance with the number of 






HANDBOOK ON ENGINEERING. 



885 



lamps in service. At h another set of transformers are used to 
develop low voltage secondary currents, which pass through a 
rotary converter i, and are converted into a continuous current to 
feed the incandescent lamps at J. 

The diagram 53 illustrates the arrangement of circuits and 
apparatus for long distance transmissions, which may range all 
the way from five or six miles up to one hundred or more, the 
greatest distance covered up to date being 145 miles. To trans- 
mit current to great distances with a small loss in the trans- 
mission lines, it is necessary to use very high voltages, ranging 
from 10,000 to 60,000, and as it is not advisable to construct 




Fig. 53. 



generators to develop such high pressures, raising transformers 
are employed to develop the line current. These transformers are 
shown in Fig. 53 at a. The generator develops currents at 1,000 
volts, and this passing through the primary coils of the trans- 
formers at a induces secondary currents which may have any 
voltage desired, say, 20,000. These secondary currents pass to 
the transmission lines b b, which may extend a distance of ten, 
twenty or more miles and may deliver all their energy at the end 
of the line or drop part of it at intermediate points. The trans- 
formers at c and also those at I develop secondary currents of 
any lower voltage that may be required ; thus, those at c develop 
secondary currents for the circuits d, which may be of, say, 1,000 
volts. The motor e is shown connected directly with cZ, but 



886 HANDBOOK ON ENGINEERING. 

motor g and lamps i, 7c require a still lower voltage, hence the 
currents in d are passed through a second set of transformers at 
/, 7i and j. The three transformers at I develop secondary cur- 
rents of sufficiently low voltage to be passed through the rotary 
converter m, and thus provide a continuous current for the trolley 
road as shown. 

STARTING. 

When the armature is turning, see that the oil rings in the 
bearings are in motion. When the machine is up to speed and all 
switches are open, lower the brushes on the commutator and col- 
lector, making sure that each bears evenly and squarely on the 
surface. Turn the rheostat until all resistance is in, then close 
the switch in the exciter circuit. Set the exciter brushes properly 
and adjust the voltage of the exciter to the proper point. 

The alternator rheostat may then be turned gradually over until 
the proper alternating voltage is indicated. The main circuit of 
the machine may now be closed. The commutator brushes should 
be adjusted at a non-sparking position. If there is any load the 
voltage should increase slightly. If it decreases, it shows that 
the series coils and the separately excited coils are opposing each 
other, unless this decrease is caused by a drop in speed. If it is 
found that the coils are opposing each other, unclamp the brush- 
holder yoke of the alternator and move its commutator brushes 
backward or forward one and one-half segments in a three-phase 
machine, and one segment in a two-phase machine. A position 
giving maximum voltage will be found from which any motion, 
forward or backward, diminishes the voltage. Having once de- 
termined the correct setting of the brushes, they may generally 
remain unchanged, unless the generator is subject to great varia- 
tion of load when in some machines, slight movements may be 
found desirable. 



HANDBOOK ON ENGINEERING. 887 

PARALLEL RUNNING OF ALTERNATORS. 

TYPES SUITABLE FOR PARALLEL OPERATION. 

If the speeds are exactly adjusted, any two alternators of the 
same frequency will operate together in parallel. The maximum 
angular displacement that may take place between two machines 
in parallel without causing objectionable phase difference decreases 
with increased number of poles. For this reason high frequen- 
cies are, generally speaking, less favorable to parallel operation 
than lower frequencies. Machines of the highest frequencies 
ordinarily used can, however, be successfully run in parallel if 
the mechanical arrangements are suitable. 

DIVISION OF LOAD. 

Machines to operate in parallel must run at such speeds as will 
give exact equality of frequency. If the prime mover running 
one machine tends to produce "a lower frequency than that run- 
ning the other, the machines cannot carry equal loads. 

When two alternators operate in parallel, each must carry an 
amount of load proportionate to the power received from its prime 
mover. If one engine or water-wheel governs in such a manner 
as to give more power than the other, this machine must carry more 
load, no matter what the field excitation may be. If under such 
conditions the field excitations are correct, both machines will de- 
liver current to the line in approximately the proportions in which 
they receive power from their prime movers. If the field adjust- 
ments are incorrect, there will be idle currents between the machines 
in addition to the currents which go to the line. 

COMPOUND ALTERNATORS. 

When compound alternators are operated in parallel, equalizer 
connections should be used so that the rectified alternating 



330 HANDBOOK ON ENGINEERING. 

current can properly distribute itself into the fields of all the 
machines. Without equalizers, an unstable condition may exist 
which will render parallel operation unsatisfactory. This 
applies particularly in the case of machines driven from the 
same source of power. The greater the amount of compounding, 
the greater will be the tendency to instability. 

BELTED MACHINES. 

If two machines are belted to separate prime movers, their 
parallel operation is dependent upon the governing of the prime 
movers. If they are belted to the same source of power, their 
parallel operation depends upon the proportions of pulleys and 
belts, and upon the tension and friction of the latter. Under 
such conditions the pulleys and belts must be adjusted with great 
nicety, so that both machines will tend, with proper belt tension, 
to run at exactly the same frequency. Even where pulleys are of 
exactly the correct dimensions, a slight difference in the thick- 
ness of belts may cause considerable cross currents or unequal 
division of load. 

DIRECT COUPLED MACHINES. 

With such machines, engines must not only be adjusted to 
run at synchronous speed, but must also be provided with fly- 
wheels large enough to prevent appreciable variations of fre- 
quency within each revolution. Inequalities of speed, due to 
insufficient fly-wheel effect, will cause periodic cross currents 
between dynamos, or will entirely prevent their operation in 
parallel. The greater the number of poles in a direct coupled 
machine, the less the angular speed variation necessary to cause 
trouble. 

High speeds are much more desirable with direct coupled alter- 
nators than low speeds, and low frequencies present less diffi- 



HANDBOOK ON ENGINEERING. 889 

culties than high. The desirabilty of high speeds with direct 
coupled alternators cannot be too strongly stated. While an 
increase of fly wheel effect will equalize the angular irregularities 
of an engine's motion, it cannot bring about such good results 
as would be brought about by a similar reduction of angular 
error effected through an increase of speed. While the large fly- 
wheel steadies the motion,' it may tend to prevent correction of 
the angular error through the effect of the cross currents. Cross 
currents which flow in machines having light fly-wheels may have 
an effective tendency to hold them together ; while machines with 
very heavy fly-wheels may tend to act independently of each 
other as far as angular variations are concerned. 

These matters should be carefully considered in installing 
direct connected alternators. Where engines operate at the same, 
speed and have the same number of cranks, this trouble can 
sometimes be overcome by synchronizing the engines themselves so 
that the impulse in both come together. When the fly-wheel 
effect is insufficient, the frequency will fluctuate and this fluctua- 
tion may cause serious trouble if synchronous motors Or rotary 
converters are connected to the circuit. When the cranks of two 
engines coupled to alternators are synchronized, any fluctuation of 
frequency which is due to lack of fly-wheel effect will still exist, 
although it may not affect parallel running. 

Where alternators have to be operated in parallel by engines to 
which they are directly coupled, it is generally desirable to use 
engines having as many cranks as possible, so that the crank 
efforts will be well distributed throughout the revolution, and 
will not tend to produce an irregularity of motion. 

STARTING. 

When a machine driven by a separate engine is thrown in 
parallel with others which are carrying load, the throttle should 
be partly closed so that it can just run at synchronous speed with- 



890 HANDBOOK ON ENGINEERING. 

out carrying load. After it is in step with the other machines, 
load can gradually be taken on by giving it more steam. If this 
is carefully done the voltage on the circuit is' not disturbed by the 
addition of the new machine. 

When a belted machine is to be thrown into parallel with others 
driven by the same shaft, its belt tension should first be reduced, 
which will tend to admit enough slip to bring it into step with 
the loaded machines. After it is thrown in it will gradually take 
load as the belt is tightened. 

SHUTTING DOWN. 

In shutting down machines operating singly, both the gener- 
ator and exciter field resistance should be cut in by turning the 
rheostat before the line switch is opened. 

When two or more generators are running in parallel on the 
bus-bars, one may be shut down at any time. The equalizer 
switch should be opened first, then the load reduced by throttling 
the engine or by slacking the belt. As soon as the load is prac- 
tically off, open the main switch. 

CARE OF MACHINES. 

With high voltage machines it is absolutely essential that they 
be kept scrupulously clean. Small particles of copper or carbon 
dust, may be sufficient to start a disastrous arc. 

The commutator collector should receive careful attention and 
be wiped thoroughly every day. 

From time to time the machine should be thoroughly over- 
hauled and given a coating of air-drying japan after cleaning. 
Machines of the rotary field type are so constructed that it is a 
comparatively easy matter to get at every part of the armature 
coils. In a large station it is recommended that an air compres- 
sor be installed so that a hose can be led to the machine and the 
dust thoroughly blown out. 



HANDBOOK ON ENGINEERING. 891 

It is advisable to have rubber mats in front of high tension 
switchboards and on the floor at the commutator-collector end of 
the generator. If it is necessary to adjust the brushes while the 
machine is in operation, the attendant should stand on the mat 
and it is also recommended that he wear rubber gloves. 

Both commutator and collector rings require a very slight 
amount of vaseline. In applying it a dry stick with a little 
chamois leather tied to one end may be used, so that there will be 
no danger of coming in contact with the brushes. 

With the brushes properly set and all screws firmly tightened 
into place, the generators should require very little attention 
while running. It is well to note from time to time whether the 
oil rings are working properly. 



ALPHABETICAL INDEX. 



Armature cores, 23, 27. 
Armature winding, 27, 29. 
Armature, arrangement of the field 

and, 33. 
Ammeters, the, 60. 
Ampere, the, 73. 
Armature, to remove the, 74. 
Assembling the parts, 74. 
Assembly, to complete the, 74. 
Armature, effect of displacement 

of, 94. 
Automatic regulator, etc., 108. 
Ammeter, 125. 
Arc lamps, 125, 151. 
Arc dynamo, the Thomson-Houston, 

131. 
Arc dynamos, installation of, 131. 
Arc lighting system, connections 

for, 133. 
Arc dynamo, controller for an, 135. 
Air blasts and jets on L. D. and 

M. D. dynamos, 141. 
Arc lamp, view of interior of M., 

150. 
Arc lamps, connections forM. &K., 

152. 
Arc lights, repairing, testing, etc., 

153. 
Automatic cut-off engines, 339. 
Armington and Sims engine, and 

setting the valves of same, 275. 
Automatic lubricators, 310. 



Automatic cut-off engine, card from 
an, 350. 

Attendants, instructions for boiler, 
532. 

Acids, pumping, 579. 

Ammonia, a few tests for, 629. 

Ammonia, effect of on pipes, 631. 

Ammonia, to charge the system 
with, 632. 

Automatic stops for electric ele- 
vators, 733. 

Auxiliary valves, hydraulic ele- 
vator, 775. 

Air compressors, losses in, 800. 

Air compressors, capacity of, 
800. 

Air compressor, the McKierman, 
801. 

Air compressor, the Bennett auto- 
matic, 803. 

Air compressor, the Ingersoll-Ser- 
geant, 803. 

Air lift system, the Pohle, 807. 

Alternating current machinery, 815. 

Alternating currents, the principles 
of, 815. 

Alternating currents, diagrams rep- 
resenting a generator of either 
continuous or, 817. 

Alternating currents and e.m.fs., 
diagrams showing the relations 
between, 821-825. 

(893) 



894 



Alternating currents, why they vary 
etc., 825. 

Alternating current circuits, induc- 
tive action in, 834. 

Angle of lag between the current, 
etc., 837. 

Alternating current generators, 
852. 

Alternating current generator, dia- 
gram illustrating a simple, 854. 

Alternator of the multipolar type, 
855. 

Alternating current generators, how 
they are run, 859. 

Alternators connected in parallel, 
starting, 860. 

Armature, the effect of displace- 
ment of the, 94, 98. 

Amperes, per motor, table, 169, 170. 

Amperes, per lamp, table, 173. 

Alternator of the multipolar type, 
855. 

Alternator, a revolving field, 857. 

Alternator, an inductor, 858. 

Alternating current generators, 852. 

Alternators run in parallel, 860. 

Alternators connected in parallel, 
starting, 861. 

Alternators, compensating and com- 
pounding, 864. 

Alternating current distributions, 
882. 

Alternators, parallel running of, 
887. 

Alternators, compound, 887. 

Brushes, why set differently, etc., 
36. 37. 

Brushes, setting, on a 4-pole ma- 
chine, 40. 



Brushes, setting, on an 8-pole ma- 
chine, 41. 

Building, to wire a large, etc., 58, 
60. 

Breakers, circuit, 62, 63. 

Bearings, filling the, 74. 

Brushes, why they spark, 82, 84. 

Brush arc lamps, connections for 
improved, 128. 

Brasses, connecting rod, 189. 

Bearings, the main, 190, 192. 

Boilers, priming in, 329, 648. 

Boiler, the steam, 398. 

Boilers, energy stored in steam, 
400, 401. 

Boilers, special high pressure, 
401. 

Boilers, types of, 402. 

Boilers, horse power of, 402, 404. 

Boilers, the rating of, 404. 

Boilers, working capacity of, 405, 
406. 

Boiler tests, code of rules for mak- 
ing, 407, 414. 

Boilers, and boiler material, defl- 

* nitions as applied to, 415. 

Boiler, selection of a, 422, 425. 

Boiler trimmings, 426, 432. 

Boiler, care and management of a, 
433, 437. 

Boilers, water for use in, 438, 448. 

Boiler, use and abuse of the steam, 
449, 453. 

Boilers, design of steam, 454, 455. 

Boilers, forms of steam, 456. 

Boilers, setting steam, 456, 457. 

Boilers, defects in the construction 
of steam, 457, 459. 

Boilers, improvements in steam, 
459, 461. 



INDEX. 



895 



Boiler surfaces, strength of stayed 
flat, 473. 

Boiler stays, 474, 477. 

Boilers, pulsation in steam, 487. 

Boilers, water columns for, 489. 

Boiler, the water-tube sectional, 
502. 

Boiler setting and furnace, view of, 
513. 

Boilers, vertical tubular, 514, 521. 

Boilers, table of pressures, allow- 
able in, 516. 

Boiler settings, fire line in, 520. 

Boiler setting, number of bricks 
required for, 522. 

Boiler, specifications for a sixty- 
inch 6-inch flue, 524. 

Banking fires, 531. 

Boiler attendants, instructions for, 
532. 

Boilers, rules and problems anent 
steam, 536. 

Blake steam pump, the, 555. 

Blake pump, operation of the, 556. 

Boiler for a steam pump, selecting, 
580. 

Brine system, 622. 

Brine, the preparation of, 624. 

Buildings, insulation of, 626. 

Boilers, foaming in, 648. 
Boiler, in case of low water in a 
649. 

Boilers, rating by feed water, 676 

Bevel wheels, 707. 

Belt driven elevators, 716, 725. 

Brake, the elevator machine, 720. 

Brake magnet, the safety, 739. 

Belts and how to care for them, 786. 

Belts, the driving power of, 788. 

Belting, strain or tension on, 788. 



Belting, rules and problem sanent, 

788, 797. 
Belts, extracts from articles on, 

790. 
Belts, transmitting power of, 795. 
Belts, table of horse-power of, 796, 

799. 
Belting, directions for adjusting, 

798. 
Bennett automatic air compressor, 

803. 

Cores, the armature, 23, 27. 

Circuits, distributing, 47. 

Constant potential, generators of 
the, 47, 48. 

Circuit breakers, 62, 63. 

Current, the strength of an elec- 
tric, 73. 

Candle power, 73. 

Commutator, care of, 75. 

Commutator gives trouble, if the, 76. 

Commutator brushes, why they 
spark, 82, 84. 

Current, the way it is shifted, 84, 
85. 

Commutated coil, etc., if the, 86. 

Controller, diagram showing con- 
nections of Brush, 118. 

Controller for arc dynamo, view of, 
135. 

Commutator segments and brush 
holders, 138. 

Cut-off in parts of the stroke, table 
of, 183. 

Crank-pins, 188. 

Connecting rod brasses, 189. 

Centers, to find the dead, 195. 

Compound engine, view of tandem, 
198. 



896 



Compound engine, the "Westing- 
house, 293. 
Cylinder lubrication, 309. 
Cut-off, view of a slide valve engine 

showing point of, 321. 
Compression begins, view showing 

the position of slide valve, when, 

321, 322. 
Card from a throttling engine, 

347. 
Card from an automatic cut-off 

engine, 350. 
Calculating mean effective pressure, 

351. 
Curve, the theoretical, 353, 357. 
Card from a Corliss engine, 357. 
Card, a stroke, 358. 
Card, a steam chest, 359. 
Cards, eccentric out of place, 360, 

361. 
Cards, eccentric, 361, 365. 
Cards from " Eclipse " ice machine 

plant, 371, 373. 
Corliss engine, how to increase the 

power of a, 381, 382. 
Code of rules for making boiler 

tests, 407, 414. 
Centrifugal force, 501. 
Cocks, proper location of gauge, 

521. 
Compound pump, the Worthington, 

544. 
Cameron steam pump, the, 548. 
Corrosion in water pipes, 579. 
Condenser, function of the pump 

and, 621. 
Cold, mechanical, easily regulated, 

622. 
Cold, utilizing the, 622. 
Capacity, unit of, 624. 



Compressor, view of the u Eclipse,' 

£35. 
Compressor pumps, 636. 
Compressor, view of double acting, 

640, 644. 
Chimneys, 688, 794. 
Chordal pitch, to find the, 69^1 703. 
Curves of teeth, 705. 
Circuit connections, view "* of, 734. 
Coils, cutting out the series field, 

737. 
Car, how to start the, 743. 
Car switch, the, 748. 
Cable switch, the slack, 749. 
Cables and how to care for them, 

783. 
Cylinder, contents of same in cubic 

feet for each foot in length, 801. 
Compressor, the McKierman air, 

801. 
Compressor, The Bennett auto- 
matic air, 803. 
Compressor, The Ingersoll-Ser- 

geant Air, 803. 
Current machinery, alternating, 

815. 
Currents, the principles of alternat- 
ing, 815. 
Currents, diagrams representing a 

generator of either continuous or 

alternating, 817. 
Currents and e.m.fs., diagrams 

showing the relations between 

alternating, 821, 825. 
Currents vary, etc. , one reason why 

alternating, 825. 
Curves are used, etc., diagrams 

showing the way in which sine, 

826. 
Currents, polyphase, 832. 



897 



Currents, etc., unbalanced three- 
phase, 834. 

Current circuits, etc., inductive 
action in alternating, 834. 

Current, etc., the angle of lag be- 
tween the, 837. 

Conu msers, etc., by the use of, 840. 

Cond* sers, etc., the general prin- 
ciple ^f construction of a, 841. 

Current generator, diagram illus- 
trating a simple alternating, 854. 

Current generators are run, how 
alternating, 859. 

Currents, field magnetizing, 867. 

Converters, rotary, 878. 

Dynamos, general directions for 

starting, 76, 77. 
Dynamos to full speed, bringing, 77. 
Dynamo with another, connecting 

one, 78. 
Dynamos into circuit, switching, 78. 
Dynamos, how connected together, 

78. 
Dynamos in parallel, 79. 
Dynamos and motors,, directions 

for running, 80. 
Dynamos, precautions in running, 

81. 
Dynamo or motor, heating in a, 

93, 94. 
Dynamo, view of the Thomson- 
Houston standard arc, 131. 
Dynamos, installation of arc, 131. 
Dynamo, view of controller for an 

arc, 135. 
Dynamos, diagrams showing best 

position of air blasts and jets on 

L D and M D, 141. 
Dead centers, to find the, 195. 



Down draft furnace, the, 503, 522, 
Deane steam pump, the, 546. 
Duplex pump, how to set the steam 

valves of a, 567. 
Decimal equivalents of 16ths, 32ds, 

and 64ths, of an inch, table of, 

583. 
Decimal equivalents of one foot by 

inches, 714. 
Decimal equivalents of an inch, 787. 

Electrical Machinery, the ele- 
mentary principles of, 1. 

Electromagnetic induction, the 
principles of, 14, 22. 

Electromotive in volts, force, etc., 
the, 63. 

Electric motors, 64. 

Electric light conductors table, 
176. 

Electric current, etc., the strength 
of an, 73. 

Engine, the steam, 177. 

Engine, the selection of an, 177. 

Expansion, the gain by, 183. 

Engine, care and management of a 
steam, 185. 

Engine, lubrication of an, 186. 

Engine, selecting an oil for an, 187. 

Engines., knocking in, 189 to 190. 

Engines, repairs of, 191. 

Eccentric straps, 192. 

Engines, automatic, 194. 

Engine, view of a tandem com- 
pound and its foundation, 198. 

Engine, how to line an, 199, 203. 

Engine, view of a twin tandem 
compound; showing arrangement 
of piping, 200. 

Engine, horse power of an, 252. 



898 



Engines, general proportions of, 
252. 

Engine, view of the Russell, 254. 

Engine, setting the valves of a 
Russell, 254. 

Engine, view of Porter-Allen, 258. 

Engine, description of the Porter- 
Allen, 259, 271. 

Engine, directions for setting the 
valves and running Porter-Allen, 
271, 273. 

Engine, the Armington and Sims, 
275. 

Engine, the Harrisburg, 276. 

Engine, the Mcintosh and Sey- 
mour, 281. 

Engine, the Ideal, 283. 

Engine, the Westing-house com- 
pound, 293. 

Engine, view of a slide valve 
(showing point of taking steam), 
321. 

Engin , view of a slide valve 
(showing the point of cut-off), 
321. 

Engines, condensing, 232. 

Engines, slide valve, 337. 

Engines, regular expansion, 338. 

Engines, automatic cut-off, 339, 
340. 

Engines, the difference in the action 
of throttling and automatic en- 
gines, 375, 379. 

Engines, economy of steam, 380. 

Engine, how to increase the power 
of a Corliss, 381, 382. 

Engine, how to increase the power 
of a throttling, 383. 

Engine, how to increase the power 
of a shaft governor, 385. 



Engine, how to line an (with a 
shaft placed at a higher or a 
lower level), 385, 387. 

Engine, how to line an (with a 
shaft to which it is to be coupled 
direct, 387. 

Engine, rules and problems apper- 
taining to the steam, 392, 395. 

Engine, to find the water consump- 
tion of a steam, 395, 397. 

Engine, best economy in running 
an, 650. 

Expansion of steam, 654. 

Engine, taking up lost motion m 
an, 654. 

Engines, feed water required for 
small, 676. 

Electric elevators, 716. 

Elevators, electric, 716. 

Elevator, the Otis, 716. 

Elevators, belt driven, 716, 725. 

Elevators, direct connected, 717, 
730. 

Elevator machine brake, the, 720. 

Elevator, view of connections of 
gravity motor cont-roller to, 722. 

Elevators, electric control, for pri- 
vate house, 749. 

Elevators, the Sprague Electric 
Co.'s, 756. 

Elevator, view of operative circuits 
for Sprague screw, 762. 

Elevators, care of Sprague, 765. 

Elevators, directions for the care 
and operation of electric, 765. 

Elevators, hydraulic, 769. 

Elevators, how to pack hydraulic- 
vertical cylinder, 769. 

Elevator, view of Otis vertical hy- 
draulic, 772. 



899 



Elevators, care of Hale, 777. 

Elevators, water for use in hy- 
draulic, 778, 781. 

Elevator inclosures and their care, 
782. 

Elevators, lubrication for hydraulic, 
785. 

Force, magnetic lines of, 6. 

Force, lines of, 6, 14. 

Force, magnetic, 13. 

Field and armature in a two-pole 

machine, general arrangement 

of, 33, 36. 
Fly-wheel, the, 184. 
Fly-wheels, rules for weights of, 

253. 
Flues, riveted and lap welded, 

477. 
Flues, table of allowable steam 

pressure on, 478. 
Force, centrifugal, 501. 
Furnace, the down draft, 503. 
Fire-line in boiler settings, 520. 
Fires, banking, 531. 
Friction of water in pipes, loss by, 

588. 
Foaming in boilers, 648. 
Feed-water required fo«r small en- 
gines, 676. 
Feed-water, heating, 676. 
Feed-water, rating boilers by, 676. 
Feed-water and steam, weights of, 

677. 
Feed-water heaters, 678. 
Feed-water heaters, gain by use of, 

680. 
Field coils, cutting out the series, 

737. 
Fluid, soldering, 101. 



Generators and motors,, two-pole, 
27, 30. 

Generators of the constant poten- 
tial, 47, 48. 

Generators of the shunt type, the 
switch board arranged for two, 
49. 

Generators and«motors, instructions 
for installing and operating slow 
and moderate speed, 74. 

Governor, the steam engine, 183- 
194. 

Governor, specifications for cen- 
trally balanced centrifugal iner- 
tia, 273. 

Governor, the Gardiner spring, 341. 

Governor, the Gardiner standard, 
342. 

Gauges, steam, 489. 

Gauge-cocks, proper location of, 
521. 

Gears, horse power of, 695. 

Gearing, wheel, 698. 

Gear-wheel, pitch line of a, 698. 

Gear-teeth, stress on, 705. 

Gearing, construction of, 706. 

Gears, calculating the speed of, 710. 

Gauges, wire, 175. 

Horse-power, 185, 238. 
Harrisburg engine, the, 276. 
Hyperbolic logarithms, table of, 397. 
Heat and steam, 416. 
Heating surface in square feet, table 

of, 501. 
Hooker steam pump, the, 553. 
Hancock inspirator, directions for 

connecting and operatingthe, 597. 
Heating feed-water, 676. 
Heaters, feed-water, 678. 



900 



Heat, units of, required to convert 
one pound of water, etc., 679. 

Horse-power of gears, 695. 

Horse-power of shafts, 697. 

Hydraulic elevators, 769. 

Hydraulic vertical cylinder eleva- 
tors, how to pack, 769. 

Hydraulic elevators, water for use 
in, 778. 

Hydraulic elevators, lubrication 
for, 785. 

Ideal engine, the, 283. 

Indicator, a few remarks on the, 
345. 

Indicator, the use of, in setting 
valves, 346. 

Iron per lineal foot, weight of 
square and round, 488. 

Instructions for boiler attendants, 
532. 

Ignition points of various sub- 
stances, 589. 

Injector and inspirator, the, 591. 

Injector, the first appearance of the, 
592. 

Injectors, general directions for 
piping, 594. 

Injectors, care and management of, 
599. 

Inspirator, directions for connect- 
ing and operating, 597. 

Insulation of buildings, 626. 

Insulation, perfect, 628. 

Iron, table of weight of a square 
foot of sheet, 712. 

Ingersoll-Sergeant air compressor, 
the, 803. 

Inductive action in alternating cur- 
rent circuits, etc., 834. 



Induction, mutual, 842. 
Ice-making plant, a complete, 639, 

640. 
Incandescent wiring tables, 160 to 

168. 
Insulation resistance, 100. 

Journals, heating of, 193. 
Joints, maximum pitches for riveted 

lap, 466. 
Joints, double riveted lap, 467. 
Joints, single riveted lap, 469. 

Knocking in engines, 189. 
Knowles, steam pump, the, 550. 

Lines of force, magnetic, 6. 

Lines of force, 6, 14. 

Lamps, connections for improved 
brush arc, 128. 

Lighting system, diagram of con- 
nections for arc, 133. 

Leads, table of, 140. 

Lamps, instructions for the instal- 
lation and care of arc, 151. 

Lamp, view of interior of M arc, 150. 

Lamps, starting the, 152. 

Lamps, diagram of connections for 
M andK arc, 152. 

Lights, instructions for repairing, 
testing, and adjusting arc, 153. 

Lubrication of an engine, 186. 

Lubricators, automatic, 310. 

Link motion, setting a plain slide 
valve with, 313. 

Lining an engine with a shaft placed 
at a higher or lower level, 385. 

Lining an engine with a shaft to 
which it is to be coupled direct, 
387. 






901 



Logarithms, table of hyperbolic, 

397. 
Lap joints, maximum pitches for 

riveted, 466. 
Lap joints, double riveted, 467. 
Lap joints, single riveted, 469. 
Lubrication of refrigerating ma- 
chinery, 630. 
License, some practical questions 

usually asked of engineers when 

applying for, 646. 
Lead, what is valve, 653, 666, 668. 
Lap on a valve, what is, 654, 666, 

670. 
Lost motion in an engine, taking 

up, 651. 
Line shaft, instructions for lining 

up extension to, 672. 
Lamps are connected, the way in 

which synchronizing, 863. 
Load, division of, 887. 

Magnet, a permanent, 1 to 2. 

Magnet, two-bar, 3 to 6. 

Magnet needle, a, 3. 

Magnetic lines of force, 6. 

Magnetic force, 13. 

Magnet, to find the lifting capacity 

of a, 13. 
Motors, two-pole generators and, 

27. 
Multipolar machines, 38,39. 
Motors, electric, 64. 
Motors and their connections, 64, 

73. 
Motors, instructions for installing 

and operating slow and moderate 

speed generators and, 74. 
Motors, directions for running 

dynamos and, 80. 



Meter for station use, view of, 149. 
Meters, Watt, 150., 151. 
Main bearings, the, 190. 
Mcintosh and Seymour engine, 281. 
Mcintosh and Seymour engine, how 

to set the valves of a, 281. 
Miscellaneous pump questions and 

answers, 559, 603. 
Meter, the Worthington water, 581. 
Machines for ice making, rating, 

638. 
Metals, melting points of, 687. 
Manila rope, transmission of power 

by, 714, 812, 813. 
Motor controller, view of connec- 
tions of gravity, 723. 
Magnet, the safety brake, 739. 
Machines, the proper care of, 739, 

779. 
Motor, the pilot, 763. 
Metric system, the, 809. 
McKierman air compressor, 801. 
Mutual induction, 842. 
Motors, induction and other types 

of, 871. 
Motor, principle of the induction, 

872, 877. 
Motors, three-phase induction, 877, 

878. 
Machines, belted, 888. 
Machines, direct coupled, 888. 
Machines, care of, 890. 

Needle, a magnet, 3. 
Noise in dynamos, 91, 92. 

Otis elevator, the, 716. 

Otis vertical hydraulic elevator and 

valve chamber, view of, 772. 
Otis gravity wedge safety, 777. 



902 



Precautions in running dynamos, 
81. 

Personal safety, 81. 

Polarity, reversal of, 142. 

Plug switchboard, standard for 6 
circuits, 148. 

Piston packing, 187. 

Pins, crank, 188. 

Piping, arrangement of, etc., 200. 

Power, what is, 251. 

Porter- Allen engine, view and de- 
scription of the, 258., 273. 

Power plant, taking charge of a 
steam, 323. 

Priming in boilers, 329. 

Pipes, loss of heat from uncovered 
steam, 391. 

Pressure allowable on flues, 478. 

Pipe, table of wrought-iron welded, 
486. 

Pressures allowable in boilers, 
table of, 516. 

Pump, the steam, 544. 

Pump, the Worthington compound, 
544. 

Pump, the Deane steam, 546. 

Pump, the Cameron steam, 548. 

Pump, the Knowles steam, 550. 

Pump, the Hooker steam, 553. 

Pump, the Blake steam, 555. 

Pump questions and answers, mis- 
cellaneous, 559, 603. 

Pump, how to set the valves of a 
duplex, 567. 

Pipe connections, proper, 569. 

Pipe connections, view of, 570. 

Pumps refusing to lift water, 
577. 

Pipes, corrosion in water, 579. 

Pumping acids, 579. 



Pump, selecting a boiler for a 

steam, 580. 
Pipes, loss by friction in water, 588. 
Pump and condenser, function of, 

621. 
Pumps, compressor, 636. 
Pipe arrangement for vaults, 637. 
Practical questions usually asked, 

etc., 646. 
Pumps do not work, reasons why, 

647. 
Priming in boilers, 648. 
Piping, simplicity in steam, 674. 
Pipe to order, cutting, 675. 
Pure water, 681. 
Prime movers, 697. 
Pitch line of a gear wheel, 698. 
Pitch, to find the chordal, 699, 703. 
Pinion, to find the proportional 

radius of a wheel or, 700. 
Pinion, to find the diameter of a,700. . 
Pinion, to find the number of revo- 
lutions of a wheel or, 700, 701. 
Pinions, a train of wheels and, ,701. 
Pitches of wheels, table of, 704.' 
Pilot motor, the, 763. 
Pressure tanks, to find leaks in, 786. 
Pohle air lift system, the, 807. 
Polyphase currents, 832. 
Piston, to test a (for leakage of 

steam, 669. 
Power factor, 870. 

Regulators for Brush arc genera- 
tors, 120 to 125. 

Rod brasses, connecting, 1S9. 

Repairs of engines, 191. 

Rules for weights of fly-wheels, 253. 

Russell engine, view of the, 240, 
254. 



903 



Regular expansion engines,, 338. 

Rules and problems appertaining to 
the steam engine,, 392, 395. 

Riveted seams, strength of, 461, 466. 

Riveted lap joints, max mum 
pitches for, 466, 469. 

Rules and problems aneut steam 
boilers, 536. 

Rules and problems anent the 
steam pump, (503, 617. 

Refrigeration, mechanical, 619. 

Rating of ice machines in tons 
capacity, 623. 

Ratings, difference in the, 623. 

Refrigerating machinery, lubrica- 
tion of, 630. 

Refrigeration, process of mechan- 
ical, 633. 

Rating .machines for ice making, 
638. 

Refrigerating plant, a complete, 
642. 

Reasons why pumps do not work, 
647. 

Rating boilers by feed water, 676. 

Rope, the main hand, 721. 

Resistance, the starting, 735. 

Rope, standard hoisting, 783. 

Rules and problems anent belting, 
788, 797. 

Rope transmission, 714, 812, 813. 

Ropes, horse power transmitted by 
hemp, 813. 

Ropes, to test the purity of hemp, 
814. 

Rope data, wire, 814. 

Rheostat, diagram of, connections 

for, 134. 
\ Rotary transformers and convert- 
ers, 878. 



Rotary transformer, principle of 

the, 879. 

Switch boards, 76. 

Starting the generator, 76. 

Sparking, 87, 91. 

Switchboard for 6 circuits, 147. 

Switchboard^ view of back of, 

148. 
Starting the lamps, 152. 
Steam engine, care and manage- 
ment of the, 185. 
Selecting an oil for an engine, 187. 
Straps, eccentric, 192. 
Steam power plant, taking charge 

of a, 323. 
Steam power plants, economy in, 

327, 329. 
Steam, high pressure, 332, 335. 
Steam, using same full stroke, 335, 

337. 
Slide valve engines, 337. 
Steam engines, economy of, 380. 
Slide valve, how to set in a hurry, 

388. 
Slide valve, the travel of a., 390. 
Steam pipes, loss of heat from 

uncovered, 391. 
Steam, heat and, 416, 421. 
Seams, strength of riveted, 461, 

466. 
Stayed flat boiler surfaces, strength 

of, 473. 
Stays, boiler, 474, 477. 
Steam gauges, 489, 490. 
Safety valves, 491, 499. 
Safety valve rules,, 497. 
Steam jets for smoke prevention, 

542. 
Smoke prevention, 542. 



904 



Substances, ignition points of vari- 
ous, 589. 

Steam, expansion of, 654. 

Steam, weights of feed water and, 
677. 

Steam, the temperature and pres- 
sure of saturated, 684. 

Something for nothing, 686. 

Stacks, weight of steel smoke (per 
lineal foot), 694. 

Shafts, table of the horse power of, 
697. 

Stress on gear teeth, 705. 

Screw, the worm, 708. 

Sheet-iron, table of weight of a 
square foot of, 712. 

Screw-cutting, 713. 

Switch, the motor starting, 719. 

Stops, automatic, 733. 

Switch lever, the 736. 

Switch, the car, 748. 

Switch, the slack cable, 749. 

Sprague Electric Co.'s elevators, 
756. 

Sprague screw elevator, view of 
operative circuits for, 762. 

Sprague elevators, care of, 765. 

Steam, the force of, etc., 398, 400. 

Starting direct coupled machines, 
886, 889. 

Shutting down, 890. 

Soldering fluid, 101. 

Two-bar magnet, 3, 6. 

Two-pole generators and motors, 

27, 30. 
Thomson-Houston standard arc 

dynamo arranged for right hand 

rotation, view of, 131. 
Table of leads, 140. 



Table of cut-off in parts of the 
stroke, 183. 

Fitting a slide valve, 191. 

Theoretical curve, the, 353, 357. 

Throttling and automatic engines, 
374, 379. 

Travel of a slide valve, 390. 

Types of boilers, 402. 

Trimmings, boiler, 426,432. 

Table of allowable steam pressure 
on flues, 478, 479. 

Tubes, thickness of material re- 
quired for, 481, 486. 

Table of the rise of safety valves, 
494. 

Table of heating surface in sq. ft. 
501. 

Table of water pressure due to 
height, 582. 

Tanks, capacity of, in U. S. gal- 
lons, 584. 

Testing for water in ammonia, 629. 

Taking up lost motion in an engine, 
654. 

Table showing the units of heat 
required to convert one pound of 
water at the temperature of 32° 
F. into steam at different pres- 
sures, 679. 

Table showing the gain by the use 
of feed water heaters, etc., 680. 

Temperature and pressure of sat- 
urated steam, the, 684. 

Table of diameters and pitches of 
wheels, 704. 

Teeth, curves of, 705. 

Teeth of wheels, proportions of, 
709. 

Tooth, to find the depth of a cast 
iron, 709. 



905 



Tooth, to find the H. P. of a, 710. 

Transmission of power by manila 
rope, 714, 812, 813. 

Table of transmission of power by 
wire ropes, 715, 814. 

Tanks, to find the leaks in, pres- 
sure, 786. 

Transmitting power of belts, 795. 

Table of horse power of belts, 796, 
799. 

Thermometers, 811. 

Transformers, 844. 

Transformer, the action in a, 846. 

Transformers, the object in using, 
849. 

Tables, incandescent wiring, 160 to 
168. 

Table of amperes per motor, 169, 
170. 

Table of volts lost at different per 
cent drop, 171, 172. 

Table of amperes per lamp, 173. 

Table of copper wire, 174. 

Table of wire gauges, 175. 

Table of electric light conductors, 
176. 

Table of carrying capacity of wires, 
99, 101. 

Table of properties of water be- 
tween 32° and 212° Fah., 679. 

Unbalanced three-phase currents, 

etc., 834. 
Useful information, 786. 

Valve, fitting a slide, 191. 

Valve setting for engineers, 318, 

322. 
Valve, the travel of a slide, 390. 
Valves, safety, 491, 499. 



Valve lead, what is, 653, 666, 668. 

Valve gear, describe the Corliss 
engine, 654. 

Valve, what is lap on a, 654, GG(>, 
670. 

Valve motion, direct and indirect, 
668. 

Valves, how to pack vertical hy- 
draulic elevator cylinder, 771. 

Volts lost at different per cent 
drop, 171, 172. 

Watt, the, 73. 

Watt meters, connections for, etc., 

149. 
Watt meters, 150. 
Work, what is, 251. 
Westinghouse engine, the, 293, 

301. 
Water consumption of an engine, 

to find the, 395. 
Water columns for boilers, 489. 
Water column connections, proper, 

515. 
Worthington water meter, the, 

581. 
Water, weight of, 585. 
Water, cost of, 587. 
Water may be wasted, how, 589. 
Wheel, to find the diameter of a, 

699. 
Wheel, to find the number of teeth 

for a, 699. 
Wheel, to fiud the circumference 

of a, 700. 
Wheels, bevel, 707. 
Worm screw, 708. 
Wiring for private houses, view of, 

750. 
Wiring tables, 160 to 168. 



906 



INDEX. 



Wire, approximate weight of 
" O. K." triple braided weather 
proof copper, 174. 

Wire gauges, difference between, 
175. 



Wires, table of carrying capacity 

of, 99, 101. 
Water, table of properties of 

water, etc., 002. 



Zigzag rivetin; 
ing, 468, 472. 



and chain rivet- 



